Nearly a year after federal investigators unveiled a sweeping investigation into the black market sales of stolen catalytic converters, three relatives in Sacramento have pleaded guilty to their role in the scheme.

Tou Sue Vang, 32, and his brother Andrew Vang, 28, pleaded guilty Monday, along with their mother, Monica Moua, 58, to “conspiring to transport stolen catalytic converters from California to New Jersey in return for over $38 million in wired payments,” according to a statement from the U.S. Attorney’s Office.

Tou Sue Vang pleaded guilty to 39 additional money laundering charges, according to the statement from the court of the Eastern District of California.

The three relatives were among 21 defendants charged with stealing, dealing and processing the converters in November 2022 by the Eastern District of California and the Northern District of Oklahoma.

“With California’s higher emission standards, our community has become a hot bed for catalytic converter theft,” U.S. Atty. Phillip A. Talbert of the Eastern District of California said at the time.

He said that about 1,600 catalytic converters were stolen in California monthly in 2021, with the state accounting for 37% of nationwide catalytic converter theft claims.

The Vang brothers and their mother pleaded guilty to a scheme to operate “an unlicensed business from their residence in Sacramento,” in which they “bought stolen catalytic converters from local thieves” and sent them to an auto parts company in New Jersey, the U.S. attorney’s office said.

They sold more than $38 million in stolen catalytic converters, which DG Auto Parts in New Jersey then allegedly processed — alongside stolen converters from other states — removing precious metals that were sold to a metal refinery for more than $600 million, according to the indictments.

The indictments alleged that the shipments from Sacramento to New Jersey began in October 2019 and continued until October 2022, with several payments in excess of $100,000.

The suspects were being recorded by confidential informants, the indictments said.

Catalytic converters are a part of a vehicle’s exhaust system that reduces the amount of pollutants and toxic gases discharged by the internal combustion engine. The devices contain precious metals such as palladium, platinum and rhodium in their cores and are often targeted by thieves because of their high value, lack of identifying markings and relative ease of theft.

The Sacramento residents are not yet scheduled to be sentenced, but could face prison time and fines up to “twice the gross gain or loss from the crimes,” the U.S. attorney’s office said.

Times staff writer Gregory Yee contributed to this report.