Mexican President Claudia Sheinbaum on Monday called for an investigation into a deadly accident that killed four officials, including two U.S. Embassy staff members, during an operation targeting suspected drug laboratories.

The crash occurred over the weekend in the northern state of Chihuahua, when a vehicle carrying the two U.S. personnel and two Mexican officials from the state’s investigation agency plunged into a ravine, according to local authorities.

Officials said the group had been returning from an operation aimed at dismantling clandestine drug labs in a remote area and were leading a convoy of five vehicles at the time.

Sheinbaum said her administration is working to determine why the operation proceeded without what she described as required federal authorization, raising concerns about potential violations of Mexico’s National Security Law.

“I want to understand why this situation occurred,” she said, adding that her government had no prior knowledge of direct collaboration between U.S. Embassy personnel and state-level authorities in Chihuahua.

The U.S. staff members were reportedly involved in training activities as part of ongoing bilateral cooperation efforts. Their identities have not been publicly released.

The crash also claimed the lives of the director of the Chihuahua State Investigation Agency and another agency member.

Sheinbaum expressed condolences to the victims’ families and said her government is in contact with the U.S. Embassy.

“We deeply regret this accident and extend our full solidarity and support,” she said.