An investigation by an undercover federal agent who posed as a buyer of looted art came to a climax with coordinated raids on four Southern California museums early Thursday, reports the Los Angeles Times.

The raids suggested that several Los Angeles art institutions may be involved in the extensive purchase of objects believed to have been taken illegally from China, Myanmar, and Thailand, as well as from Native American sites within the United States, according to search warrants served Thursday.

Authorities were most concerned with artifacts allegedly taken from Thailand’s Ban Chiang archaeological site, and suggested that they were smuggled into the United States and donated at inflated prices, thereby allowing collectors to claim fraudulent charitable deductions on their tax returns.

The newspaper said it is possible museum staff members may be indicted for complicity in the looting schemes under American law.

The museums that were investigated in the raid were the Los Angeles County Museum of Art; the Pacific Asia Museum, in Pasadena; the Bowers Museum, in Santa Ana; and the Mingei International Museum, in San Diego.

Museum officials denied wrongdoing and pledged to cooperate fully in the investigations.