Four Minnesota men have been charged in federal court with operating a catalytic converter theft operation worth millions of dollars.

The conspiracy yielded roughly $21 million total in payments to the defendants, the Department of Justice said in the indictment unsealed Tuesday.

The four defendants are: John Charles Kotten, 41, of Hutchinson; Justin Tyme Johnson, 32, of St. Paul; James Dillon Jensen, 34, of Minneapolis; and Soe Nye Moo, 31, of St. Paul. They were charged Oct. 18.

They operated this scheme between May 2020 and October 2022, the DOJ said in the indictment. The goal of the scheme was to transport stolen catalytic converter parts from Minnesota and elsewhere and sell them to buyers. These car parts can be worth thousands of dollars.

Catalytic converter thefts have been a rising problem in Minnesota and nationwide in recent years, and thieves will often sell them to someone before they are melted down for their valuable metals.

Roughly $19 million of the conspiracy's revenue came from "high-volume" buyers based in New Jersey, Oklahoma, Colorado and New York, according to the charges.

Reached by phone, Kotten declined to comment on the charges. Kotten's attorney declined to comment on the case. Mark Kelly, an attorney for Moo, declined to discuss the charges.

"We'll address the charges in court," he said.

Attempts to reach the other defendants were unsuccessful.

People the DOJ referred to as "cutters" would allegedly steal the car parts throughout Minnesota using saws and power tools before transferring them to the defendants as a part of the scheme, charges say.

Prosecutors accused the men of purchasing "junk cars" to make it seem like they were part of a legitimate car scrapping and recycling business if they were investigated and needed to explain their income.

The defendants were given conditional releases Tuesday before their next court appearance.

The four are facing charges for conspiracy to transport stolen property across state lines, along with separate individual charges. Moo was charged with possessing a machine gun.

Kotten and Johnson are also charged with transporting stolen property, conspiracy to commit money laundering, and with making false statements to a financial institution. Johnson was also charged with conspiracy to commit money laundering.