Federal authorities announced charges against a ring of nine people for thefts of millions of dollars worth of paintings, sports memorabilia and other valuables including an Andy Warhol silkscreen, a Jackson Pollock painting and nine World Series rings belonging to the late Yankees catcher Yogi Berra.

The thefts took place over more than two decades at 20 museums, institutions and stores across Pennsylvania, New Jersey, New York, Massachusetts, Rhode Island, Washington, D.C., and North Dakota, the U.S. attorney for the Middle District of Pennsylvania said Thursday.

Investigators believe some of the sports memorabilia and other items had been melted down, including nine of Berra’s 10 World Series rings, U.S. Attorney Gerard M. Karam said at a news conference.