Two workers with Mexico’s electricity commission were killed in an armed attack in Sonora this week.

In the early morning hours Tuesday, four electricity commission workers in two company trucks were returning from a repair job in a rural area of Sonora when they were ambushed on the highway in the municipality of Onavas by armed assailants.

Two of the workers — Juan Francisco Encinas and Luis Dionisio Figueroa Hernandez — were killed in the attack, and one of the vehicles was left entirely burned. The other two men were able to hide, according to officials with the federal prosecutor’s office, which has opened an investigation into the murders.

On Wednesday, Gov. Alfonso Durazo put out a statement promising that the case would be solved and those responsible punished. Officials say they are still determining what occurred, but believe members of the cartel group La Linea confused the workers for rival gang members in the region.

On Thursday, Mexican President Andrés Manuel López Obrador added that the workers could have been targeted for repairing power lines that were cut by the cartels. The electricity commission has previously admitted that there are areas of Mexico where it is unable to carry out its work because of safety concerns.