Twelve Mexican federal police have been detained in an investigation of how two U.S. Embassy employees were wounded after being caught up in a police chase on the outskirts of the capital, authorities said on Monday.

Attorney General Marisela Morales said a judge had ordered the officers remain in custody for 40 days. They have not been charged with any offense in Friday's incident but she said prosecutors were looking into possible abuse of authority.

"We are not ruling out any kind of wrongdoing or any line of investigation," Morales told reporters. "We are asking for them to be detained so that we have the time necessary to conduct an exhaustive investigation."

Officials said on Friday police fired on the embassy workers' vehicle, which had diplomatic license plates, after the driver veered out of the way when he saw the officers' weapons.

The latest incident took place on a highway on the southern outskirts of Mexico City close to the city of Cuernavaca, which has been ravaged by criminal gangs during the government's conflict with drug cartels.

Roadside shootings have been a feature of the violence linked to drug gangs that has overshadowed President Felipe Calderon's six years in office. Gangs have been known to set up fake military checkpoints to ambush rivals.

Last year, two U.S. Immigration and Customs Enforcement agents were shot by hitmen on a major Mexican highway. One of the agents died.

There have been more than 55,000 drug related killings, including those of 3,000 police officers, in Mexico since Calderon took office in late 2006.

Earlier this month, all 348 federal police officers at Mexico's international airport were replaced after police there shot dead three fellow officers in an alleged drug related killing. Three officers have been charged.