Two stolen hand-carved religious artifacts, sandstone lintels dating back to the 9th and 10th centuries, were returned to the Thai government on Tuesday in a ceremony more than 50 years overdue.

The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — roughly a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum.

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Thai and U.S. officials participate in a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

Thai and U.S. officials participate in a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)
A lentil originally from the Nong Hong Sanctuary in Thailand is displayed during a ceremony to return it and another stolen hand-carved sandstone lintel dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

A lentil originally from the Nong Hong Sanctuary in Thailand is displayed during a ceremony to return it and another stolen hand-carved sandstone lintel dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)
A lentil originally from the Khoa Lon Sanctuary in Thailand is displayed during a ceremony to return it and another stolen hand-carved sandstone lintel dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

A lentil originally from the Khoa Lon Sanctuary in Thailand is displayed during a ceremony to return it and another stolen hand-carved sandstone lintel dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)
Tatum King, left, special agent in charge of Homeland Security Investigations in San Francisco, shakes hands Mungkorn Pratoomkaew, right, Consul-General of Thailand in Los Angeles, during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

Tatum King, left, special agent in charge of Homeland Security Investigations in San Francisco, shakes hands Mungkorn Pratoomkaew, right, Consul-General of Thailand in Los Angeles, during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)
Manasvi Srisodapol, Ambassador of Thailand to the United States, speaks during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

Manasvi Srisodapol, Ambassador of Thailand to the United States, speaks during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)
David A. Prince, Special Agent in Charge Homeland Security Investigations in Los Angeles, speaks during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

David A. Prince, Special Agent in Charge Homeland Security Investigations in Los Angeles, speaks during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)
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Thai and U.S. officials participate in a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

Thai and U.S. officials participate in a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

A lentil originally from the Nong Hong Sanctuary in Thailand is displayed during a ceremony to return it and another stolen hand-carved sandstone lintel dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

A lentil originally from the Nong Hong Sanctuary in Thailand is displayed during a ceremony to return it and another stolen hand-carved sandstone lintel dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

A lentil originally from the Khoa Lon Sanctuary in Thailand is displayed during a ceremony to return it and another stolen hand-carved sandstone lintel dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

A lentil originally from the Khoa Lon Sanctuary in Thailand is displayed during a ceremony to return it and another stolen hand-carved sandstone lintel dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

Tatum King, left, special agent in charge of Homeland Security Investigations in San Francisco, shakes hands Mungkorn Pratoomkaew, right, Consul-General of Thailand in Los Angeles, during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

Tatum King, left, special agent in charge of Homeland Security Investigations in San Francisco, shakes hands Mungkorn Pratoomkaew, right, Consul-General of Thailand in Los Angeles, during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

Manasvi Srisodapol, Ambassador of Thailand to the United States, speaks during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

Manasvi Srisodapol, Ambassador of Thailand to the United States, speaks during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

David A. Prince, Special Agent in Charge Homeland Security Investigations in Los Angeles, speaks during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

David A. Prince, Special Agent in Charge Homeland Security Investigations in Los Angeles, speaks during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

San Francisco, which owns the museum, agreed to hand over the ancient sandstone slabs, which had been structural parts of two religious sanctuaries in northeastern Thailand, following a three-year investigation by the U.S. Department of Homeland Security and a civil lawsuit.

Thai and U.S. officials participate in a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

Thai and U.S. officials participate in a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

Records showed that the lintels had been obtained by a collector in galleries in London and Paris in the 1960s, according to the civil complaint. The collector, Avery Brundage, was apparently aware that at least one of the lintels had been illegally taken out of Thailand, the complaint states. Brundage, a former controversial president of the International Olympic Committee who donated the art to establish the museum, died in 1975.

The Thai government had been trying to get the museum to return the artifacts since 2016, to no avail. The Los Angeles Times reported the mystery surrounding the lintels, and various attempts to return them to Thailand, in March.

The San Francisco city attorney did not immediately return a request for comment on Tuesday.

A lentil originally from the Nong Hong Sanctuary in Thailand is displayed during a ceremony to return it and another stolen hand-carved sandstone lintel dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

A lentil originally from the Nong Hong Sanctuary in Thailand is displayed during a ceremony to return it and another stolen hand-carved sandstone lintel dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

U.S. officials stressed the importance of repatriating stolen cultural artifacts. The repatriation ceremony, which included Thai dancers and prayers, was held in Los Angeles because the consulate is in the city — which also has the largest Thai population in the U.S.

The Thai ambassador to the U.S., Manasvi Srisodapol, called the ceremony part of the lintels' “sacred journey back home" and acknowledged the ongoing illegal trade of Thai artifacts in the black market.

“I do wish that the story of the Thai lintels will help raise public awareness to prevent removal of historic, religious and cultural treasures form their original sites in local communities," he said.

A lentil originally from the Khoa Lon Sanctuary in Thailand is displayed during a ceremony to return it and another stolen hand-carved sandstone lintel dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

A lentil originally from the Khoa Lon Sanctuary in Thailand is displayed during a ceremony to return it and another stolen hand-carved sandstone lintel dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

David Keller, the Homeland Security Investigations special agent who oversaw the repatriation case for nearly four years, said officials believe European dealers illegally exported the lintels out of Thailand. The antiquities' combined estimated value is $700,000.

Tatum King, the special agent in charge for HSI in San Francisco, said the case reinforces the need for museums and art collectors to inventory their items and see if any are in fact stolen artifacts.

“Museums are often the front line of this and we need their help,” King said.

Tatum King, left, special agent in charge of Homeland Security Investigations in San Francisco, shakes hands Mungkorn Pratoomkaew, right, Consul-General of Thailand in Los Angeles, during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

Tatum King, left, special agent in charge of Homeland Security Investigations in San Francisco, shakes hands Mungkorn Pratoomkaew, right, Consul-General of Thailand in Los Angeles, during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)
Manasvi Srisodapol, Ambassador of Thailand to the United States, speaks during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

Manasvi Srisodapol, Ambassador of Thailand to the United States, speaks during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

 David A. Prince, Special Agent in Charge Homeland Security Investigations in Los Angeles, speaks during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)

David A. Prince, Special Agent in Charge Homeland Security Investigations in Los Angeles, speaks during a ceremony to return two stolen hand-carved sandstone lintels dating back to the 9th and 10th centuries to the Thai government Tuesday, May 25, 2021, in Los Angeles. The 1,500-pound (680-kilogram) antiquities had been stolen and exported from Thailand — a violation of Thai law — a half-century ago, authorities said, and donated to the city of San Francisco. They had been exhibited at the San Francisco Asian Art Museum. (AP PhotoAshley Landis)