A coroner said his office was conducting an autopsy to determine whether one of the two victims of the Asiana Airlines crash at San Francisco International Airport was run over and killed by an emergency vehicle.

San Mateo County Coroner Robert Foucrault said San Francisco Fire Department officials notified him and his staff at the crash site on Saturday that one of the two Chinese girls who died may have been struck on the runway.

"We were made aware of the possibility at the scene that day," Foucrault said, adding that he did not get a thorough look at the victims on Saturday to see if they had external injuries.

One of the bodies was found on the runway near where the plane's tail broke off upon impact, he said. The other was found on the left side of the aircraft about 9 meters away from where the Boeing 777 came to rest after it skidded down the tarmac and not far from an emergency slide.

San Francisco Fire Chief Joanne Hayes-White did not return telephone calls from The Associated Press. Earlier on Sunday, Hayes-White had said she did not know if the two dead girls were alive when her crews arrived at the scene.

She told the San Francisco Chronicle on Sunday, however, that the girl found on the side of the airplane had injuries consistent with having been run over.

"As it possibly could have happened, based on the injuries sustained, it could have been one of our vehicles that added to the injuries, or another vehicle," she told The Chronicle.

"That could have been something that happened in the chaos. It will be part of our investigation."

Foucrault said the autopsy, which he expects to be completed by Monday, will involve determining whether the girl's death was caused by injuries from the crash or "a secondary incident”.

The teenagers' families are expected to arrive in San Francisco on Monday, and they will receive the autopsy results before they are made public, he said.

The coroner said both girls were pronounced dead at the airport.

Chinese media and Asiana Airlines have identified the girls as Ye Mengyuan and Wang Linjia, students from Zhejiang province.

They were part of a group of 29 students and five teachers from the school who were heading to summer camps in California, according to education authorities in China.

While speaking to reporters at San Francisco General Hospital on Sunday, San Francisco Mayor Ed Lee called the questions being raised about a rescue vehicle possibly striking one of the victims "unsubstantiated".

"It was very, very hectic when they arrived minutes after the plane came to rest and there was smoke coming out, and people were trying to get out as quickly as they could," Lee said.