Fiat Chrysler Automobiles has been fined $30 million for paying off union leaders for negotiation concessions.

Over a period of eight years, UAW officials received more than $3.5 million in cash and valuable items through a training center jointly run by FCA. Prosecutors revealed that the head of FCA labor relations, Al Iacobelli, executed the scheme with five UAW officials and a spouse and in 2014, eliminated a $262,000 home mortgage with training center money, the Detroit Free Press reports.

U.S. District Court Judge Paul Borman sentenced FCA US to three years’ probation and ordered an independent compliant monitor in his ruling. This came after FCA pleaded guilty in March to one count of conspiring to violate the Labor Management Relations Act.

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Assistant U.S. Attorney Erin Shaw told Judge Paul Borman that FCA’s guilty plea was especially significant as many corporate cases like these result in deferred prosecutions.

“We’ve been informed by our colleagues at the Department of Labor in Washington that this case marks one of the largest violations of the Taft-Hartley Act in United States history, if not the largest,” Shaw said. “The criminal conduct by FCA and its executives has significantly undermined the confidence and trust that the men and women working in the plants and on the assembly lines hold in their leaders. These crimes have also undermined the workers’ trust in the integrity of the collective bargaining process.”

The training center was initially established in the 1980s to train workers “but over time, the training center’s benevolent purpose was usurped by a corrupt one,” Shaw added. “The training center served as a conduit for many of the illegal payments at issue in this case.”