MEXICO CITY -- Mexican prosecutors charged 14 federal police officers Friday with trying to kill two CIA agents and a Mexican navy captain in an August ambush south of the capital.

The announcement by the Attorney General's Office did not state a motive for the attack, but said the officers had been charged with attempted homicide and damage to property.

Mexican authorities initially had said the attack was probably an accident by well-intentioned police officers who thought they were shooting at criminals. Later, however, U.S. and Mexican officials who spoke to The Associated Press on condition of anonymity said they were leaning toward the idea that it was a targeted attack masterminded by a drug cartel.

Since then, Attorney General Marisela Morales had acknowledged that her office was investigating whether organized crime was behind the attack.

An official with the Attorney General's Office said the police officers were on duty at the time of the shooting and required to be wearing uniforms and driving official vehicles. Instead they wore civilian clothes and drove private cars when they fired 152 bullets at the U.S. Embassy vehicle that was heading to a military training camp.

"They should have been in their uniforms and in the patrol unit. That was strange," said the official, who spoke on condition of anonymity because he was not authorized to speak with journalists.

He said investigators were still trying to determine whether a drug cartel planned the attack.

The U.S. vehicle tried to escape and more vehicles joined the aggressors in the chase as the police officers continuously shot the diplomatic vehicle. The two CIA men were wounded, but survived. The navy captain was not injured.

A prosecutors' statement said the fact that the U.S. vehicle was armoured helped the men survive.

Prosecutors said the shooters changed into uniforms and arrived in police patrol cars after they were called in for questioning hours after the Aug. 24 shooting.

Homicide and attempted homicide charges are usually state crimes in Mexico, but the Mexican official said this was a more serious case because the suspects were federal police.

The Mexican officers have spent nearly 80 days under a form of house arrest that Mexico uses in organized crime cases.