The United States filed its first labor complaint against Mexico under the United States-Mexico-Canada Agreement on Wednesday over alleged tampering with union votes at a General Motors plant in Mexico.

U.S. Trade Representative Katherine Tai invoked a “rapid response” mechanism under the pact, which allows for expedited enforcement of collective bargaining and free association rights.

The complaint takes issue with a vote of approval last month for a collective bargaining agreement between GM’s Mexico division and the Miguel Trujillo López union.

The vote, which was announced on April 5, was suspended by Mexican officials over “concerns about irregularities, including the destruction of ballots,” the complaint said.

The U.S. is asking for a review of "all actions and statements, by or on behalf of the Union or the Company, with respect to the legitimization process, including any action or statement contributing to the denial to any worker of the right to a personal, free, and secret vote on the legitimization of the collective bargaining agreement,” according to the complaint. 

Mexico said it received the U.S. trade representative’s complaint, and would “conduct a review of the alleged denial of rights to workers at the General Motors plant in Silao, Guanajuato,” according to Reuters.

Workers were deciding whether to recognize the union that has long controlled its labor contract. Authorities stopped the vote after inspectors found that at offices where the union had boxes ballots were destroyed, making them unable to be counted, according to The Associated Press.

Democratic Reps. Bill Pascrell (N.J.), Dan Kildee (Mich.) and Earl Blumenauer (Ore.) raised concerns about the vote in a letter to GM on Tuesday.

Pascrell praised the U.S.’s move on Wednesday, saying in a statement that the reported acts “clearly violates the renegotiated NAFTA.”

“It’s refreshing how seriously the Biden Administration is taking the rights of labor and how swiftly it is standing up for workers’ right to freely associate and choose an independent union,” he said.

GM said in a statement to The Hill that it supports "the rights of our employees to make a personal choice about union representation and any collective bargaining on their behalf." 

"GM condemns violations of labor rights and actions to restrict collective bargaining. We do not believe there was any GM involvement in the alleged violations and have retained a third-party firm to conduct an independent and thorough review," the company continued. "The company will cooperate with the U.S. Government and the Mexican Labor Ministry and other stakeholders to protect the integrity of the process.”

Updated: May 13 at 11:04 a.m.