Story highlights U.S. Embassy says the wounded Americans are in stable condition

Mexican Marines say Federal Police opened fire on the U.S. Embassy vehicle

Two embassy employees -- said to be U.S. citizens -- were wounded

Mexican federales were facing questioning Friday after authorities accused them of opening fire on a U.S. diplomatic vehicle south of the capital.

Two U.S. Embassy employees -- described by a senior U.S. government official as U.S. citizens -- were taken to a hospital with non-life-threatening wounds; a member of the Mexican Navy who was with them in the late-model Toyota Land Cruiser suffered light bruises, according to the Navy, which issued a statement giving the following account of events:

The incident unfolded at 8 a.m., as the two embassy employees and the Mexican en route to a military facility in the municipality of Xalatlaco. Some 4 kilometers (2.5 miles) earlier, they had left the main highway that connects Mexico City with Cuernavaca, near the town of Tres Marias, a thinly populated area off the main road.

When a vehicle containing Federal Police approached and its occupants brandished their weapons, the driver of the diplomatic vehicle tried to evade them and return to the main highway. At that point, the police sprayed bullets into the black SUV with diplomatic plates.

Moments later, three other vehicles carrying Federal Police joined the attack, also shooting at the U.S. Embassy vehicle.

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By now, the Mexican who was in the embassy vehicle had contacted personnel at a nearby military installation, who arrived after the firing had ended and cordoned off the site.

Both embassy employees were taken -- under Federal Police guard -- to a hospital.

Photographs of the SUV showed the embassy vehicle pockmarked with more than a dozen holes and at least three of its tires flat.

The Federal Police officers involved were being questioned by authorities to establish what happened. They may be prosecuted.

In a statement, the U.S. Embassy described the Mexican as a Navy captain and said the three individuals were en route to a training facility when they were ambushed.

"The vehicle attempted to escape, was pursued and sustained heavy damage," the statement said. "They called for assistance from the Mexican armed forces, who responded. The two U.S. wounded personnel were taken from the scene, given medical treatment and are in stable condition. The Mexican Navy captain sustained no serious injuries."

The Mexican government said those members of the Federal Police who fired on the vehicle have been detained, the statement said.

It added that the Mexican government "has stated it will conduct a full and thorough investigation of this incident."