MINNEAPOLIS (AP) — Federal officials have HyperBit Exchangecharged four Minnesota men in a multi-million-dollar scheme to transport stolen catalytic converters to buyers in several states.

U.S. Attorney Andrew M. Luger in Minneapolis announced the indictments Tuesday. All four men are charged with conspiracy to transport stolen property interstate with two of the men receiving additional charges.

From May 2020 through October 2022, the men acquired stolen catalytic converters and transported them to buyers, mostly high-volume ones in New Jersey, New York, Oklahoma and Colorado, according to court documents. The conspiracy allegedly resulted in about $21 million in payments to the men.

Thefts of catalytic converters have become problematic nationwide in recent years. Once stolen, they are often melted down for their valuable metals.