General Motors Co (GM.N) workers in Mexico were on track to scrap the contract negotiated by one of the country’s biggest unions, according to a Mexican government report on a vote last month that led to a U.S. complaint under a new North American free trade deal. On Wednesday, the Biden administration called for a probe into allegations that worker rights were denied at GM"s Silao pickup truck plant during the vote to ratify workers" collective contract with the Confederation of Mexican Workers (CTM). Mexican President Andres Manuel Lopez Obrador on Thursday said he accepted the U.S. recommendation to make sure there would be no fraud in union votes, noting that many "irregularities" had been detected in the union-led vote at GM. The CTM, which represents 4.5 million workers, is one of several traditional unions accused by workers and activists of putting business interests over workers" rights. read more A ministry report into the vote, reviewed by Reuters, shows that 1,784 workers cast ballots against keeping the CTM contract, while 1,628 workers voted to maintain it. Allegations of interference - including the ministry"s findings that some blank ballots in union possession were cut in half - have raised suspicions among some activists and experts that the CTM may have been headed for a deeper defeat. A follow-up vote, which the Labor Ministry ordered to take place within 30 days, could result in a wider margin against keeping the current contract, especially if more workers who were apathetic or scared of voting turned out the second time, said Alfonso Bouzas, a labor scholar at Mexico"s National Autonomous University. "This whole new opportunity is going to awaken conscience and interest," Bouzas said. CTM"s national spokesman, Patricio Flores, said the union supported the regional trade deal and would comply with the law and whatever "would not harm investment in Mexico." He did not dispute the vote tally in the labor ministry report, but called for an investigation into the disputed proceeding before a second vote. "We should listen to the voice of these workers and not let pressure from unions in the United States and Canada have influence right now," CTM said in a statement. The ministry document showed that just over half of the 6,494 workers eligible to vote did so in the first of two days of voting, before labor inspectors halted the process. If GM workers scrap their contract, either the CTM or a new union could negotiate new collective terms. Many collective bargaining contracts in Mexico consist of deals between unions and companies without workers" approval, which has helped keep Mexican hourly wages at a fraction of those in the United States. The United States-Mexico-Canada Agreement, which took effect last year and replaced the 1994 NAFTA, sought to strengthen worker rights in Mexico and slow migration of U.S. auto production south of the border. GM has said it respects the rights of its employees to make decisions over collective bargaining, and that it was not involved in any alleged violations. It declined to comment on the Labor Ministry report. GM has indicated that it is ready to shift away from the old system that had let companies in Mexico turn a blind eye to worker rights, said Jerry Dias, the head of Canada"s largest private sector union, Unifor. "The rules are changing and a company like GM is not going to get caught," he said. Dias said he hoped to personally monitor the follow-up vote at the Silao plant. Contract ratification votes are required under Mexico’s 2019 labor reform, which underpins the renegotiated free trade pact, to ensure workers are not bound to contracts that were signed behind their backs.