April 20 (UPI) — Two employees of the U.S. Embassy in Mexico and two Mexican law enforcement officers were killed in a car crash over the weekend while returning from an operation to destroy laboratories in the northern state of Chihuahua, officials said.

The four people were traveling in a vehicle when they skidded off the road and into a ravine at about 2 a.m. Sunday, Chihuahua Attorney General Cesar Jauregui Moreno told reporters in a press conference.

He identified the deceased as Agency Director Pedro Roman Oseguera Cervantes and officer Manuel Genaro Mendez Montes of the Chihuahua State Investigation Agency and two instructor officers from the U.S. Embassy, whose names have not been made public.

“From here, we extend our deepest condolences and wish peace and resignation to the families of those who died in this unfortunate accident,” he said.

U.S. Ambassador Ronald Johnson to Mexico offered his condolences online.

“We honor their dedication and tireless efforts to confront one of the greatest challenges of our time. Our thoughts and prayers are with them and their loved ones,” he said in a statement.

“This tragedy is a solemn reminder of the risks faced by those Mexican and U.S. officials who are dedicated to protecting our communities. It strengthens our resolve to continue their mission and advance our shared commitment to security and justice, to protect our people.”

The incident occurred as they were returning from an operation that destroyed six clandestine laboratories in the municipality of Morelos, where Jauregui said synthetic drugs were being produced.

The site was located following a three-month investigation and destroyed on Friday and Saturday.

“It is one of the largest sites found in the country where chemical drugs were being produced,” Jauregui said during the press conference.