Federal agents have also focused on Barry L. MacLean, an art collector and industrialist who is a vice chairman of the Art Institute of Chicago and who maintains a museum, known as the MacLean Collection, in Libertyville, Ill., north of Chicago. Mr. MacLean is chief executive of the MacLean-Fogg Company, a manufacturer of industrial parts in nearby Mundelein, Ill.
According to the federal documents, Mr. MacLean bought artifacts looted in Cambodia, Thailand, Myanmar and Vietnam. They were sold to Mr. MacLean by Mr. Olson, who the court papers say described Mr. MacLean as one of his best clients.
Among the items in Mr. MacLean’s collection said to have been illegally taken from foreign sites were bronze caldrons and ivory and gold earrings from Cambodia, and bronze combs, bracelets and spears from Thailand.
Mr. MacLean was not named in the court papers; he was referred to only as Individual A. But his identity was confirmed by a law enforcement official and another person briefed on the investigation who spoke on the condition of anonymity.
Neither Mr. MacLean, whose involvement in the investigation was first reported by The Los Angeles Times, nor Mr. Malter responded on Tuesday to interview requests left at their offices and sent by e-mail.
A spokeswoman for the Art Institute of Chicago, Erin Hogan, said the museum had no works in its collection donated by Mr. MacLean, although he recently pledged $5 million for the endowment campaign for the Art Institute school.