Mexico President Claudia Sheinbaum said she would demand explanations after U.S. Embassy instructors died in a crash in northern Chihuahua following an operation aimed at destroying a clandestine drug lab. Speaking Monday, Sheinbaum said her government would investigate what happened over the weekend to ensure no Mexican laws were broken.

Sheinbaum’s remarks focused on how the incident unfolded and what she said her government knew about it. She told journalists that “It was not an operation that the security cabinet was aware of,” adding, “We were not informed; it was a decision by the Chihuahua government.”

The crash occurred after an operation in rural areas of Chihuahua to destroy drug labs belonging to criminal groups, according to authorities. Chihuahua Attorney General César Jáuregui said the officials died Sunday while returning from the operation, after the truck “appears to have skidded at some point and fell into a ravine, exploding,” while traveling through rugged mountain territory between Chihuahua and the state of Sinaloa.

Jáuregui said the deaths included two Mexican investigative officials and two U.S. Embassy instructors who were participating in routine “training work.” The U.S. Embassy, however, did not identify the Americans who died or which U.S. government entity they worked for, saying the officials were “supporting Chihuahua state authorities’ efforts to combat cartel operations.”

The mixed public accounts have fueled debate about the extent of U.S. involvement in Mexico’s security operations. Sheinbaum said Monday that there were no joint operations “on land or in the air” in Mexico, describing the relationship instead as information sharing within what she called a “well-established” legal framework.

Sheinbaum also said her government would provide more information once it has more details, while emphasizing that state governments must have authorization from Mexico’s federal government to collaborate with U.S. and other foreign entities “as established by the Constitution.” The statement placed additional weight on questions of legal authority at a time when U.S.-Mexico relations are under heightened pressure, including efforts by the Trump administration to crack down on cartel activity.

Mexican officials’ accounts of who was involved also shifted in the hours after the crash. Hours after authorities initially described the response, Mexico’s Security Cabinet confirmed that the army and the state prosecutor’s office carried out a joint operation over the weekend in Chihuahua dismantling drug labs in the same location, Morelos, using drones to locate the labs and finding drugs-manufacturing material but no people, who were believed to have fled.

Later, a local official backtracked and clarified to press that there “were no U.S. agents in the operation to secure the narco-lab,” and said the embassy officials joined the group after the operation, several hours away from where the action took place. The U.S. Ambassador Ronald Johnson expressed condolences on social media, while providing few details beyond the embassy’s statement that the officials were supporting Chihuahua’s anti-cartel efforts.

The episode arrives as the two countries prepare for additional talks on the U.S.-Mexico-Canada free trade agreement, with negotiations scheduled to begin in Mexico City. The U.S. delegation is led by Trade Representative Jamieson Greer, who was scheduled to meet with Sheinbaum on Monday, while the Trump administration also announced visa restrictions on family members of the Cartel de Sinaloa.

The crash also comes amid an ongoing dispute over previous U.S. security cooperation with Mexico, including earlier public statements that Sheinbaum said involved U.S. surveillance drone flights at Mexico’s request. That history has kept scrutiny high after past episodes, including the January detention in Mexico of former Canadian athlete Ryan Wedding, which both countries described differently in terms of whether it followed a binational operation.

Sources (from cluster):