Mexico City, Mexico - President Claudia Sheinbaum said Monday her government was unaware of the presence in northern Mexico of two US officials who were killed in a car accident following an anti-narcotics operation.

"We were not informed," Sheinbaum told reporters, a day after the US said two embassy employees were killed in an accident in the Chihuahua state, along with two Mexican investigators.

Sheinbaum said the US agents were on Mexican territory on the orders of the Chihuahua state government. "It wasn't an operation the [federal] security cabinet knew about," she said.

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Her administration is requesting information from the US and Chihuahua state government to examine whether there was any violation of national security, the leader said.

The state prosecutor of Chihuahua said Sunday that the four were returning from a raid of clandestine drug labs when their car, which was in a five-vehicle convoy, skidded off the road and into a ravine.

Prosecutor Cesar Jauregui said six clandestine synthetic drug labs were raided in Morelos following a three-month investigation.

The Americans killed were "instructor officers" who "were carrying out training tasks" as part of anti-drug cooperation between the US and Mexico, he said.

Writing on X on Sunday, US Ambassador Ronald Johnson said the two Americans worked at the US Embassy in Mexico.

He identified the dead Mexicans as the director of Chihuahua's State Investigation Agency and an officer with that agency.

"We honor their dedication and tireless efforts to confront one of the greatest challenges of our time," he wrote, referring to all four.

"This tragedy is a solemn reminder of the risks faced by those Mexican and US officials who are dedicated to protecting our communities," he said, adding it "strengthens our resolve to continue their mission."