A team of more than 30 FBI agents raided the property of Michigan artist Donald "D.B." Henkel this week in relation to an alleged art forgery ring that involved fake paintings sold for six-figure sums to top U.S. galleries, collectors and museums, according to the Detroit News.

Based in a rural part of Traverse City, Henkel, 60, is associated with a group spread across multiple states behind an alleged scheme to sell fakes billed as "rediscovered" works by 20th-century American artists, including Ralston Crawford, George Ault, and Gertrude Abercrombie, along with bringing fake sports memorabilia to market.

A years-long investigation into suspected mail and wire fraud conspiracy culminated with the FBI retaining a search warrant for Henkel's property on Tuesday and Wednesday and seizing items that have not yet been fully disclosed. No arrests have been made.

Buyers' concerns mounted after some of the works were researched following being purchased at auction and through other sales since 2016.

According to the Detroit News, the scam began to unravel when conservators noticed that materials used didn't exist at the time the works were allegedly created, including the pigment Hansa yellow and acrylics for a painting supposedly made in 1938. One victim became alarmed when an artist's archive showed no mention of a purchased work.

Fake yet convincing provenances were provided. For example, for Crawford’s Smith Silo, sold at auction in May 2016, Henkel claimed the work was a gift of the artist to Henry Hotz Jr., dean of arts at the Pennsylvania Academy of Fine Arts. The painting sold for $395,000 and $299,000 went to Henkel, according to reports.