MEXICAN AUTHORITIES on Tuesday ordered the General Motors Co. (GM) union in the city of Silao to repeat a worker vote following pressure from US lawmakers for the automaker to address alleged abuses that could potentially violate a new trade deal.

Mexico’s labor ministry said it found “serious irregularities” in last month’s vote, which is required under a Mexican labor reform to ensure workers are not bound to contracts that are signed behind their backs and keep wages low.

Such votes are part of Mexico’s broader effort to uphold worker rights as part of a new free trade pact that replaces NAFTA.

The concerns over GM come amid various complaints in recent days regarding Mexican workplace abuses, just as US activists and politicians begin to flex new powers to enforce labor standards south of the border enshrined in the United States-Mexico-Canada Agreement (USMCA).

The largest US labor federation, the AFL-CIO, on Monday urged the US government to file a complaint under USMCA against Tridonex, an auto-parts plant in the Mexican border city of Matamoros where it said workers have been blocked from electing an independent union.

In the GM case, some ballots were destroyed during the union-led vote, Mexico’s labor ministry found. It also said the union, which is part of the powerful Confederation of Mexican Workers (CTM), refused to give labor inspectors documentation of the vote tally.

US Representatives Dan Kildee, Bill Pascrell and Earl Blumenauer, all Democrats, called on GM to answer questions about potential abuses.

The largest US automaker “has a responsibility to speak out against violations of labor and human rights abuses at the Silao GM plant,” they said in a letter to GM Chief Executive Mary Barra.

The lawmakers also cited news reports indicating that GM officials had removed independent inspectors, among other intimidation tactics targeting workers.

GM (GM.N) has denied wrongdoing, and said government-approved inspectors were not prevented from entering the voting site. It also said it condemned labor rights violations and had hired a third-party firm to review the matter.

GM’s union must hold a new vote within 30 days, the ministry said, after the initial vote “violated principles of safety and certainty.”

Hugo Varela, head of the CTM in Guanajuato state, where the Silao plant is located, did not respond to a request for comment on the labor ministry’s order.

He previously said that CTM was committed to complying with the law and keeping jobs in Mexico.

A spokesman for the US Trade Representative’s office declined to comment on GM.

The disputed vote at Silao, which employs some 6,000 people, came several days before GM said it would invest $1 billion in an electric vehicle manufacturing complex in Mexico, triggering criticism from the United Auto Workers.

UAW spokesman Brian Rothenberg told Reuters separately this week that it was “concerned and is having appropriate discussions” about the Mexico vote.

In addition, Geneva-based IndustriALL Global Unions and Toronto-based Unifor said in letters to GM President Mark Reuss last week that the incident appeared to violate the USMCA and urged GM to protect workers.

Unifor’s president, Jerry Dias, expressed his “outrage” at the situation and said he would explore “all available avenues” to uphold worker rights in Mexico, including dispute resolution tools under the USMCA. — Reuters