Passengers aboard the airliner that crashed in San Francisco Saturday pleaded for more ambulances to show up and help the wounded, recordings of their 911 calls revealed Wednesday.
"We've been down on the ground, I don't know, 20 minutes, a half-hour," one woman said from the runway. "There are people waiting on the tarmac with critical injuries, head injuries."
"We're almost losing a woman here," she said as a 911 dispatcher tried to reassure her that help was on the way. "We're trying to keep her alive."
Late Wednesday, California Highway Patrol issued 11½ minutes of audio of some of the scores of 911 calls placed in the minutes after Asiana Airlines Flight 214 crashed upon landing at San Francisco International Airport on Saturday. Two people died and more than 180 were injured.
Deborah Hersman, chairman of the National Transportation Safety Board, said Wednesday that the doors on the plane weren't opened until about 90 seconds after the plane had come to a full stop.
Hersman said that the first fire truck was on the scene two minutes after the plane crashed and was spraying foam a minute later, the Los Angeles Times reported.
Fire officials told NBC's TODAY that its ambulances responded within 13 minutes, but added that private ambulances were already there. The incident commander initially told them to keep away from the plane because of fears it could explode.
A spokesman for American Medical Response defended the response times, saying he did not think ambulances could have got there any quicker. He said ambulances had gone to a staging area before continuing to the wreckage in groups of five in accordance with a crash response plan.
Several of the 911 callers said they didn't think there were enough emergency crews on the scene.
"We're at the San Francisco International Airport. We just got in a plane crash, and there's a bunch of people who still need help and there's not enough medics out here," another caller reported.
"There is a woman out here on the street, on the runway, who is pretty much burned very severely on the head, and we don't know what to do," the woman said. "She is severely burned. She will probably die soon if we don't get any help."
A male caller said he was at the airport and “our airplane just crashed upon landing.” He was then asked which runway he was on. “I don’t know the runway, we literally just run out of the airplane.”
“There’s a bunch of fire trucks and a couple of ambulances, there’s one or two, but there’s a lot of people hurting on the ground and we probably need people,” he said.
Toward the end of the call, the man said he could see “tons of cops and ambulances coming now.”
Jason Sorrick, the American Medical Response spokesman, said there was already an ambulance at the airport at the time of the crash and within five minutes a further two had arrived.
He said within 20 minutes there were at least 10 ambulances dispatched by AMR at the airport and, in total, 38 went to the scene.
Sorrick said nine ambulances from San Francisco Fire Department were also present, along with a number of others from Bayshore Ambulance.
He said that ambulances were initially sent to a staging area -- managed by the fire department -- that may have been out of sight of the passengers.
Sorrick said there had been an explosion on the right side of the airplane, but “as soon as that issue was addressed our units [ambulances] were moved in five at a time” to pick up patients.
He said this was to minimize the risk of chaos at the crash site and ensure that if there was another explosion “you’re not wiping out” most of the ambulances there.
“You don’t want them to go in, become injured and … themselves become patients,” he said.
“I don’t know how much quicker we could respond,” he added, saying they had acted “exactly as we are trained to do.”
Twenty of the crash victims remained in San Francisco-area hospitals on Wednesday, four of them in critical condition.
One of those critically injured is a child who is being treated at San Francisco General Hospital.
Doug Yakel, a spokesman for San Francisco International Airport, declined to comment on the emergency services' response times, referring a request to do so to the NTSB as it was "still conducting an active investigation into all aspects of the accident."
NBC News' Ian Johnston and Tom Costello contributed to this report.