Stellantis logo is seen displayed in this illustration taken, May 3, 2022.
Stellantis logo is seen displayed in this illustration taken, May 3, 2022. Reuters / DADO RUVIC

The United States has asked Mexico to probe alleged worker rights violations at a Mexican auto-parts plant owned by Italian-French carmaker Stellantis, the fourth such investigation under a revised trade deal, U.S. officials said on Monday.

The U.S. request for Mexico to look into possible rights abuses at Teksid Hierro de Mexico in the northern border state of Coahuila comes under the 2020 United States-Mexico-Canada Agreement (USMCA) that aims to improve conditions at Mexican workplaces.

Companies have been closely watching these early cases to see how tougher labor rules play out under the trade pact that replaced NAFTA. Under the USMCA, factories that violate worker rights could lose their tariff-free status on exports.

Stellantis, the world's fourth-largest auto group, did not immediately respond to a request for comment. It has previously said it respects collective-bargaining rights.

Since 2014, Teksid - which employs nearly 1,500 people and makes iron castings for heavy vehicles - has been embroiled in a union dispute that workers say has blocked them from being represented by the Miners Union and led to employee dismissals.

The AFL-CIO labor federation and the United Auto Workers union, which represents U.S. Stellantis workers, along with Mexico's Miners Union, flagged the potential violations, the U.S. Trade Representative's office said in a statement.

Labor Secretary Marty Walsh added the U.S. government aimed to work with Mexican counterparts and Teksid "to ensure that workers can choose their union representatives freely and without interference."

Mexico's Economy Ministry did not immediately respond to a request for comment.

Stellantis, formed from the merger of Peugeot maker PSA and Fiat Chrysler, runs seven other plants in Mexico and last year produced more than 400,000 vehicles in the country.

U.S. officials previously opened labor inquiries into U.S. automaker General Motors, U.S.-owned factory Tridonex and Japanese conglomerate Panasonic.