Mexican authorities charged 14 federal police officers with attempted murder over a shooting in August that wounded two US government employees, reportedly CIA agents.
The attorney general's office said on Friday the officers, who were formally placed under arrest, "attempted to take the life of two employees of the US embassy" and a Mexican navy officer who was traveling with them south of Mexico City.
The three survived a barrage of 152 bullets thanks to the armor on the US embassy's black 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 plates, but then changed into uniform and brought patrol cars when investigators arrived at the scene.
They 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.
The statement from the attorney general's office did not indicate why the federal police officers shot at the US embassy car. A spokesman for the prosecutor's office did not return calls seeking comment.
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 AFP 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.
Washington works closely with President Felipe Calderon's government against drug smuggling under the $1.6 billion Merida Initiative, providing law enforcement training and equipment, including Black Hawk helicopters.
US State Department spokeswoman Victoria Nuland said that she did not expect any changes in US cooperation with Mexican police as a result of the shooting.
"We work very hard on both sides of the border when these incidents happen to be prompt and quick in judicial proceedings and being transparent with each other and to try to correct any issues we have along the border," she said.
The US embassy cooperated in the Mexican investigation.