The Royal Ontario Museum insists it followed strict internal guidelines when it purchased a Buddhist stupa from Subhash Kapoor, a Manhattan art dealer who has since been charged by the Indian government with trafficking in stolen artifacts.

The stupa — a small stone urn used to house the remains of monks — and the ROM have now become caught up in an international investigation by U.S. immigration and security officials, who are also investigating a large illegal antiquities operation allegedly directed by Kapoor, the ROM acknowledged when queried by CBC News.

In 2004, Toronto's ROM paid Kapoor $125,000 for the miniature reliquary, money that came from private donations.

Deepali Dewan, a senior curator at the ROM, described Kapoor as a "reputable and respected dealer of South Asian art," which was a common opinion at the time among museum curators.

Dewan also provided CBC News with a redacted copy of the ownership history of the item and said she had spoken personally with the individual who claimed to have held the piece in his personal collection since 1969 — a key date when it comes to the trading of ancient relics.

CBC has since obtained an unredacted copy of the ownership document signed by the owner, Dr. Leo Figiel, a prominent U.S. collector of South Asian artifacts who died in 2013.

An ancient stone urn that is believed to have once held the remains of Buddhist monks was purchased by the Royal Ontario Museum in 2004 from a Manhattan art dealer now under investigation for dealing in stolen antiquities. (CBC)

U.S. Immigration Customs Enforcement and Homeland Security Investigations are also delving into Kapoor's antiquity empire, in an investigation they have called Operation Hidden Idols.

Since 2012, U.S. agents have seized over 2,600 artifacts valued at approximately $150 million from Kapoor's warehouses.

And last month, officials with ICE-HSI reclaimed a bronze sculpture of Shiva and Parvati from the David Owsley Museum of Art at Ball State University in Indiana.

The museum had purchased the piece from Kapoor in 2005, but ICE-HSI officials say the idol was "sourced illegally from India under the direction of Subhash Kapoor and smuggled into the United States."

In a Nov. 17 press release, ICE-HSI also said the sculpture had a "fraudulent provenance attributed to Leo Figiel," a provenance that said it was part of Figiel's private collection since 1969.

The date on the provenance is important because in 1970 a UNESCO convention came into effect that prohibited the illicit import, export or transfer of ownership of cultural property.

Investigators believe fake provenances were dated to pre-1970 in order to circumvent the law, and while U.S. officials have tracked what they say are many false provenances provided by Kapoor, the Shiva and Parvati sculpture was the first one they have found attributed to Figiel.

This raised questions about the integrity of the stupa on display at the ROM.

ROM history with Kapoor

Over the years the ROM has acquired eight items from Kapoor, either as gifts or purchases.

Investigative journalist Jason Felch believes the stunning carved stone stupa may have been stolen from a Buddhist Temple in the tribal area of Pakistan.

Felch, co-author of Chasing Aphrodite:The Hunt for Looted Antiquities at the World's Richest Museum, says the ROM should have considered any relic coming from the Gandhara region with a great deal of suspicion.

"The tribal region of Pakistan is where al-Qaeda had its base for many years and where there's been rampant looting [of relics] to fuel those groups," says Felch.

CBC asked the ROM if it had been in contact with ICE-HSI regarding the piece.

And in a joint statement dated Dec. 17, the ROM and ICE-HSI acknowledged there was an ongoing investigation and that they are "working collaboratively to establish the legitimacy of items in the museum's collection obtained through Subhash Kapoor."

If ICE-HSI requests the ROM transfer the reliquary, Dewan said the museum will have to undertake a rigorous depossession process "without fear or a knee-jerk reaction."

Kapoor's art empire

Before his arrest in 2011 in Germany, Kapoor had a 30-year reputation in the antiquity business.

He owned an upscale Manhattan gallery called Art of the Past, which specialized in South Asian antiquities, and was seen as a one-stop shop for anyone looking to buy what was then considered legitimate ancient art from India, Pakistan and Afghanistan.

A Bharhut Stupa Yaksi pillar sculpture from the Second Century B.C., India, was seized by U.S. agents in the case against former art gallery manager Aaron Friedman, who worked for Kapoor and who pleaded pleaded guilty in December 2013 for his role in an international scheme to smuggle ancient Buddhist and Hindu sculptures. (The Associated Press)

But the Indian government alleges Kapoor has been trafficking in looted Asian antiquities for years and was part of a network of temple looters operating out of the south Indian state of Tamil Nadu.

Tamil Nadu police issued a warrant for his arrest, and after he was extradited from Germany In 2012, Kapoor has been in jail in India awaiting trial.

In the meantime, the Manhattan district attorney's office charged Kapoor's girlfriend, Selina Mohamed, his sister, Sushma Sareen, and gallery manager Aaron Freedman with criminal possession of stolen property and conspiracy.

U.S. prosecutors allege that Mohamed, Sareen and Freedman have been involved in the fabrication of bogus ownership histories for dozens of objects sold to museums around the world since 1992. All three have since pleaded guilty and received various sentences.