SAN FRANCISCO -- Stunned and bleeding after a Boeing 777 crash-landed at the San Francisco airport, hundreds of passengers staggered across the debris-strewn tarmac, some trying to help the critically injured, others desperately calling 911 and begging for more ambulances as dire minutes ticked away.

"There's not enough medics out here," a caller told a dispatcher in a 911 call released by the California Highway Patrol. "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."

Two people died and 180 of the 307 people were hurt Saturday when Asiana Airlines Flight 214, coming in too low and too slow, slammed into a seawall at the end of the runway. The impact ripped off the back of the plane, tossed out three flight attendants and their seats and scattered pieces of the jet across the runway as it spun and skidded to a stop.

The battered passengers, some with broken bones, were told over the jet's public-address system to stay in their seats for another 90 seconds while the cockpit consulted with the control tower, a safety procedure to prevent people from evacuating into life-threatening fires or machinery.

"We don't know what the pilots were thinking, but I can tell you that in previous accidents there have been crews that don't evacuate. They wait for other vehicles to come, to be able to get passengers out safely," said National Transportation Safety Board Chairman Deborah Hersman.

And in this accident, it appears one of the two Chinese teens who died may have been run over by a fire truck rushing to the burning jet.

Hersman said Thursday the fuel tanks did not rupture in the crash, and that the fire was caused by oil on hot engines.

The NTSB is now wrapping up their investigation, heading back to Washington D.C. in coming days with "a mountain of information" to analyze and review, from pieces of the airliner to interview transcripts.

Many passengers jumped out the back of the plane or slid down inflated slides through emergency exits. Then, say some, an unnerving wait began.

"We walked and this lady starts to appear, really stumbling and waving her hand and yelling. It took a couple seconds to register," said Elliott Stone, who was returning from a martial arts competition in South Korea. "Then as I saw the condition she was in, I was like, oh my goodness."

The woman collapsed, he said, and he and his family realized there might be more victims nearby, "so we started running, searching for more. I believe we ended up finding four people that were in the back in the rubble, all very bad condition. We stayed with them, comforted them, yelling for ambulances, fire trucks, anyone to come help."

911 tapes recorded frantic callers, pleading for help.

"We've been on the ground, I don't know, 20 minutes, a half hour," said one woman. "There are people laying on the tarmac with critical injuries, head injuries. We're almost losing a woman here. We're trying to keep her alive."

San Francisco Fire Department spokeswoman Mindy Talmadge said Thursday that some passengers who called 911 may not have immediately seen ambulances at the scene because they were dispatched to a nearby staging area as first responders assessed who needed to be taken to the hospital.

"There is a procedure for doing it," Talmadge said. "You don't cause more chaos in an already chaotic situation. You don't do that with 50 ambulances running around all over the place."