MEXICO CITY -- Mexican federal police opened fire Friday on an armored vehicle carrying U.S. government employees, wounding two, in a confusing incident in which it wasn’t clear if the police were trying to help or harm the Americans.

The U.S. Embassy here described the incident as an ambush and said that the Mexican government “has acknowledged that members of the federal police were involved.”

But the embassy provided few details of what took place, and the Mexican government version, given in a joint statement issued by the Mexican navy and the Public Security Secretariat, left unanswered whether the police knew they were firing on a U.S. vehicle or had done so by mistake.

The shooting occurred around 8 a.m. on a wooded stretch of a mountain road and came after the embassy vehicle apparently already had escaped an ambush that had been laid by four other vehicles, according to the joint statement.

That ambush took place when U.S. personnel and an employee of the Mexican navy were headed to a mountain installation known as El Capulin. The U.S. vehicle, a gray four-door Toyota SUV, had left the main highway and had turned down a dirt road when a vehicle with armed men cut it off.

When the embassy vehicle sought to return to the main highway, the assailants opened fire. Three other vehicles carrying gunmen joined the chase, firing on the embassy vehicle.

The Mexican naval official radioed for help, and Mexican army and federal police units were summoned, the statement said.

Mexican news reports said the embassy vehicle had reached the main two-lane highway heading toward Cuernavaca, a city south of Mexico City, when federal police opened fire. Photos show that the embassy vehicle had clearly visible diplomatic license plates.

The Mexican statement did not provide an explanation for why federal police fired on the U.S. vehicle. It said the federal police involved were providing explanations to prosecutors to determine if they had criminal responsibility. The U.S. Embassy statement said “members of the federal police who were involved” had been detained.

Photographs from the scene showed that gunmen pumped at least 30 rounds into the armored SUV, bringing it to a halt in the middle of the two-lane highway, its tires punctured. The vehicle suffered crash damage to its right front.

Mexican news reports identified the U.S. employees as Stan Dave Boss, 62, and Jess Garner, 49. After the shooting, the two were taken to Cuernavaca’s Inovamed Hospital, arriving at 9:10 a.m.

“They arrived in stable condition. They were conscious,” said Mercedes Alcalde, a social worker at the hospital. She said they were transferred at 11:30 a.m. to a hospital in Mexico City.

U.S. Embassy spokesmen declined to say which federal agency the two work for or to provide details of their mission in Mexico. The embassy’s statement contained no information about the identities or positions of the injured men, but described their destination when they were ambushed as “a training facility.”

“It did not involve the DEA,” said Barbara Carreno, a spokeswoman for the Drug Enforcement Administration.

A Pentagon spokesman, Lt. Col. Tom Crosson, said the ambush was “not an event that we’re tracking,” and that the victims were not U.S. military personnel “as far as I know.”