Fourteen Mexican federal police officers have been charged with attempted murder over a shooting in August that
wounded two US government employees, reportedly CIA agents.
The officers were charged on Friday and the Mexican attorney general's office said in a statement they had been formally placed under arrest.
The statement did not indicate why the federal police officers opened fire. A spokesman for the prosecutor's office did not return calls seeking comment.
The attorney-general's office said the police officers "attempted to take the life of two employees of the US embassy" and a Mexican navy officer who was travelling with them south of Mexico City.
The three survived a barrage of 152 bullets as they were travelling in an armoured US embassy's sport-utility vehicle, prosecutors said.
The federal policemen were wearing civilian clothes and driving private cars when they shot at the SUV, which had US diplomatic licence plates. They later changed into uniform and brought patrol cars when investigators arrived at the scene.
The officers hid the civilian vehicles from which the gunmen opened fire near the town of Tres Marias "simulating circumstances that turned out false", the prosecutor's office said.
One of the federal officers was charged with making false statements while five others were accused of covering up the attack. The 14 were also charged with property damage.
The two Americans, who were identified as CIA agents by Mexican and American media, left the country shortly after the August 24 shooting.
The US government has refused to say where the two men worked.
They were heading to a military training facility when they were attacked in what the US embassy has described as an ambush.
Mexican police suggested at one point that the officers had mistakenly shot at the US embassy vehicle while investigating a kidnapping case.
But a Mexican official has told the AFP news agency that one line of investigation explored by authorities was whether the officers were working for a criminal gang and ambushed the Americans because they believed they were CIA agents.
A lawyer for two of the police officers said their legal rights were violated.
"The proof is that we asked for a face-to-face between my clients and the US diplomats, but the federal public ministry rejected our request," Enrique Rusty Mondragon Huerta was quoted as saying in El Universal newspaper.
The US works closely with President Felipe Calderon's government against drug smuggling under the $1.6bn Merida Initiative, providing law enforcement training and equipment, including Black Hawk helicopters.