Los Angeles—On January 24, 50 U.S. agents raided four museums and an art gallery in Southern California in search of evidence of illegal antiquities trading and tax fraud. The museums are the Los Angeles County Museum of Art, the Bowers Museum in Santa Ana, the Mingei Museum in San Diego and the Pacific Asia Museum in Pasadena. The five-year-long investigation tracked practices that authorities say violated the Archaeological Resource Protection Act, the National Stolen Property Act, and California state law, which bans trade in protected cultural objects. Also alleged: Tax and U.S. Customs infractions.

Search warrants provided by the U.S. Attorney in Los Angeles outlined their case—prepared with help from a National Parks Service undercover investigator—that the four museums had obtained objects from Thailand and China that were taken out of those countries illegally. The warrants also alleged that the museums acquired the objects as donations from collectors who bought them from dealers who appraised the cheaply purchased objects at inflated values so the donors could reap tax benefits.

Justice Department documents state that pottery and bowls bought in the $800 range were appraised at just under $5,000, to avoid requiring further documentation for such donations, as mandated by federal law. Not all the donations were at such a low level. Objects bought for $10,000 were appraised at $40,000, which donors deducted from their taxes.

Tom Mrozek, a spokesman for the Justice Department, says that the early morning raids and the show of force with large numbers of agents were a necessary part of law enforcement’s effort to seize computer files before potential defendants could hide or destroy them. Federal authorities believe that those files, which were not seen during the undercover investigation, could hold crucial evidence. Customs and tax violations drew agents from other branches of law enforcement.

The four museums issued statements saying that they had abided by museum collecting guidelines, and that they were working with law enforcement. “LACMA understands its critical role in researching objects before and after they come into the museum’s collection,” said director Michael Govan in a statement. “The objects in question were gifts from Jonathan and Cari Markell, longtime museum members and donors to LACMA. Following LACMA’s standard protocol, donors were required to make representations regarding ownership and each piece was studied by the curatorial staff prior to coming into the collection.”