Joe Ashton, a former vice president of the United Automobile Workers Union, has been charged with bribery and money laundering, according to court documents filed Wednesday. The now-retired Ashton is the 13th person charged in connection with the corruption scandal, and also the highest ranking.

The move by federal authorities comes just days after UAW President Gary Jones stepped aside temporarily as he also comes under scrutiny.

The scandal has tainted a union long seen as one of the cleanest in the American labor movement. And recent events have cast a cloud over ongoing contract negotiations between the UAW and Detroit’s Big Three since some officials reportedly took bribes to back off on demands during prior contract talks.

Over the last two years, an array of union officials, as well as some executives from Fiat Chrysler Automobiles and General Motors, have been charged with a variety of crimes involving kickbacks, fraud and money laundering.

Ashton was reportedly under the federal microscope for some time. His top aide, Jeff Pietrzyk, already pleaded guilty to his role in the case. The case laid out by federal prosecutors involves a variety of shady deals, including the production of $4 million worth of commemorative UAW watches. All told, he reportedly helped direct $15.8 million worth of union contracts for his personal benefit.

Ashton, who stepped down from his union post in 2014, was closely associated with other top UAW officials, including former president Dennis Williams and his successor. Those two were among a number of current and former union officials who were targeted in an FBI raid of their homes searching for additional evidence of corruption.

While neither Williams nor Jones have been charged, local news reports have speculated as to if and when they also could face indictments.

For his part, the current UAW chief announced over the weekend that he would take a paid leave of absence while the corruption probe continues. That move came as union members at Ford were set to begin voting on a new, four-year tentative contract with the automaker. Once that settlement is wrapped up, UAW bargainers will move over to Fiat Chrysler to push for an agreement there.

"The UAW is fighting tooth and nail to ensure our members have a brighter future," Jones said in a statement. "I do not want anything to distract from the mission. I want to do what's best for the members of this great union."

Concerns about the scandal have weighed heavily on both sides during the ongoing round of contract talks, according to Arthur Schwartz, a former GM negotiator and now head of Labor and Economic Associates. Union bargainers, in particular, he said, were concerned that workers might not think they were getting enough in the light of evidence that surfaced through the corruption probe. That may have contributed to the 40-day strike at General Motors, he told NBC News.

There were significant challenges facing both sides, notably including the handling of thousands of contract workers, many of whom will be able to get full time status, under the agreement finally reached with GM.

That issue is expected to also be at the forefront when talks resume at FCA, having been put on hold in September so senior union negotiators could focus on GM. But the Fiat Chrysler talks also are expected to be complicated by the automaker’s announcement last week that it plans to merge with France’s PSA Peugeot, said Schwartz, adding that the union will want to make moves now to prevent eventual job losses.