Two U.S. officials wounded last week when assailants thought to be Mexican federal police opened fire on their vehicle have left the country without giving statements to investigators, Mexico's attorney general said.

"They must first be in the appropriate conditions to be able to do it. It will be done at the right time, once they are in shape for it," Marisela Morales told reporters, adding that the U.S. government is fully cooperating with the probe.

The safety and health of the two men is the primary consideration, she said.

Neither the U.S. or Mexican government has provided any details about the wounded Americans, but The New York Times reported that both men are CIA officers.

Though 12 federal cops are being held in connection with last Friday's incident in the central state of Morelos, the Mexican attorney general said she would not discuss possible suspects "so as not to obstruct the investigation."

"It will be with scientific evidence that we will solve this very sensitive case," she said.

Morales also declined to comment on the U.S. government's description of the events as an ambush, saying only that "there are various lines of investigation."

Federal police were engaged in anti-crime operations at the time of the assault on the U.S. Embassy vehicle, a Toyota SUV with diplomatic plates, the Mexican government said last Friday in a statement.

The Americans and a Mexican navy official were traveling on a stretch of unpaved road en route to a navy installation at El Capulin mountain when they encountered "a vehicle whose occupants brandished guns," the statement said.

The driver of the Toyota "maneuvered to get away and re-enter the highway, the moment in which the occupants of the aggressor vehicle opened fire on the diplomatic vehicle."

Soon, according to the statement, "three other vehicles joined the pursuit and fired gunshots at the U.S. Embassy vehicle." EFE