Mexican President Claudia Sheinbaum said on Monday she was not aware US embassy officials were working with the northern state of Chihuahua to combat drug cartels following a car crash that killed officials from both countries.

Two US officials and two Mexican state officials died in a car crash on Sunday after an operation to destroy clandestine drug laboratories in the municipality of Morelos. Sheinbaum said her government would review whether the operation violated national security law.

State Attorney General Cesar Jauregui later on Monday told local media there had been a misunderstanding and that the U.S. officials who died did not take part in the lab raid.

“In Chihuahua there was no participation of any agent of any foreign entity in the operation,” Jauregui told media outlet Grupo Formula.

Jauregui said only Mexican personnel, around 80 in total, took part in the operation. The U.S. officials, who have not been identified, were picked up by the group after the operation at a separate location, where they had given a class on flying drones. They were being driven to the state capital when the accident occurred, Jauregui said.

Sheinbaum said during her daily morning press conference that she would ask U.S. Ambassador to Mexico Ronald Johnson to meet with Foreign Minister Roberto Velasco to discuss the incident.

The role of U.S. personnel in anti-cartel missions is highly sensitive in Mexico. Sheinbaum has repeatedly said that while intelligence sharing and security cooperation are essential to fighting organized crime, Mexico will not accept U.S. boots on the ground.

In contrast, U.S. President Donald Trump has called for greater use of U.S. military force to combat Mexican cartels.

The embassy did not immediately respond to a request for comment.

The Mexican officials killed in the accident were the director of the state’s investigation agency and an officer, state authorities said on Sunday. Ambassador Johnson, in a post on X mourning the incident, did not identify the dead U.S. embassy staff.