MEXICO CITY » Fourteen former federal police officers have gone on trial on charges of using excessive force in a 2012 shooting attack that wounded two CIA agents, Mexico’s national security commissioner said Wednesday.

Monte Alejandro Rubido said there was no evidence the police officers had acted on orders from an organized crime gang, saying the attack on the diplomatic vehicle was a case of mistaken identity.

"We identified the motive in the attack and it was a regrettable error on the part of the people there," Rubido told reporters. "The only legal evidence the investigation found was the use of excessive force on the part of the colleagues in the federal police."

He did not say when the trial process began for the defendants, who he said were being held in jail. Trials in Mexico are not public and can last for years.

Mexican officials have long said the federal police group was investigating a kidnapping when it encountered the U.S. agents and a Mexican marine captain and opened fire on their U.S. Embassy armored SUV. Officials say the plainclothes officers reported they thought they were pursuing kidnappers on a rural road.

The officers were dismissed because of the shooting, which occurred in an area just outside Mexico City where a drug gang was active.

"The day before they had detained a gang of kidnappers in the region and suddenly they saw a vehicle with unusual characteristics for the area … in a crass error, they opened fire on the vehicle, assuming it was (driven by) criminals," Rubido said.

He did not say what possible sentences the ex-officers faced if convicted. Mexico’s criminal code allows prison sentences of one to eight years for a similar offense, "abuse of authority," in cases when a public servant "in the course of carrying out their duties commits violence against a person without legitimate cause."

"There are 14 former policemen in jail, so you can see there is no tolerance for breaking the law," Rubido said.

The U.S. Embassy had no immediate comment on the announcement.