MEXICO CITY—Mexican federal police who ambushed a U.S. Embassy vehicle, wounding two CIA officers, were not investigating a kidnapping in the area, the attorney general's office said Sunday, contradicting the official police explanation of the shooting.

The CIA officers were heading down a dirt road to a military installation south of Mexico City on Aug. 24 with a Mexican navy captain when a carload of gunmen opened fire on their SUV with diplomatic plates and gave chase. More vehicles joined in the pursuit. Officials say 40 percent of the 152 shots fired at the armored SUV went through the driver and front-seat passenger side windows after it had come to a stop.

The two CIA officers, who have not been identified, received non-life threatening injuries. The captain was not injured.

Mexican federal police maintain it was a case of mistaken identity since the officers were investigating a kidnapping of a government official in the area. Police suggested the officers might not have noticed the vehicle's diplomatic plates and thought the vehicle belonged to the kidnappers.

But on Sunday assistant prosecutor Victoria Pacheco Jimenez said the federal officers charged with attempted murder in the case were not working on a kidnapping at the time.

Pacheco said there was a kidnapping but "objectively it is unrelated to the investigation."

She said the investigation has shown that it was a direct attack on the U.S. Embassy vehicle carried out by 14 federal police officers, all of whom have been detained. All the gunfire came from the federal police weapons, discounting versions that the embassy vehicle fired first.

Arrest orders were issued for four commanding officers for allegedly planning the attack and ordering agents to lie, but they have sought legal protections and remain free. A fifth commanding officer accused of covering up evidence has given his declaration to a judge and been released on bail.

Pacheco didn't give a reason for the attack.

U.S. and Mexican officials have told The Associated Press that evidence points toward an intentional attack, perhaps ordered by a drug cartel.

A senior U.S. official has said there was strong circumstantial evidence that the officers were working for organized crime in a targeted assassination attempt. He spoke on condition of anonymity.

The rural road where the attack took place near Cuernavaca is known territory of the remnants of the Beltran Leyva gang. The once-powerful cartel has been run by Hector Beltran Leyva since Mexican marines killed his brother, drug lord Arturo Beltran Leyva, in Cuernavaca in late 2009.

Prosecutors say the police officers were dressed as civilians and were in private cars at the time of the attacks.

Asked if the attack involved organized crime, Pacheco said: "The assistant attorney general's office in charge of the case does not have that line of investigation."

Federal police spokesman Jose Ramon Salinas said Sunday he had no comment.

Federal police commissioner Maribel Cervantes told the Mexican newspaper Milenio, in comments published Thursday, that she had spoken to U.S. authorities and assured them that it was not an ambush or an attack, and had presented them with documentation backing the explanation that the officers were investigating a kidnapping.

The detained police face charges of attempted homicide, damage to property, carrying restricted weapons and covering up evidence.