Fire Chief Joanne Hayes-White and Assistant Deputy Chief Dale Carnes both raised the possibility at a news conference with first responders.
"There was a possibility one of two fatalities might have been contacted by one of our apparatus at one point during the incident," Carnes said.
San Mateo County Coroner Robert Foucrault earlier said his office was conducting an autopsy to determine whether one of the victims survived the crash but was run over and killed by a responding vehicle. He said his staff was notified of the possibility by senior San Francisco Fire Department officials at the crash site on Saturday.
Remarkably, 305 of 307 passengers and crew survived the crash and more than a third didn't even require hospitalization. Only a small number were critically injured.
Investigators said Asiana Airlines Flight 214 was traveling "significantly below" the target speed during its approach and that the crew tried to abort the landing just before it smashed onto the runway. What they don't yet know is whether the pilot's inexperience with the Boeing 777 and at San Francisco's airport played a role. Officials said the probe will also focus on whether the airport or plane's equipment also could have malfunctioned.
The South Korea government said officials will inspect engines and landing equipment on all Boeing 777 planes owned by Asiana and Korean Air, the national carrier.
Investigators said the weather was unusually fair for foggy San Francisco. The winds were mild, too. During the descent, with their throttles set to idle, the pilots never discussed having any problems with the plane or its positioning until it was too late.
Firefighters said they encountered smoke, leaking jet fuel and passengers coming down on chutes when they arrived. Lt. Christine Emmons said Monday at the news conference that she and her partner ran up a chute into the plane and found four passengers trapped in the back. The conditions in the plane were changing rapidly, with the fire coming down on rescuers and the smoke thickening as the trapped passengers were pulled out to safety, she said.
Seven seconds before the Boeing 777 struck down, a member of the flight crew made a call to increase the jet's lagging speed, National Transportation Safety Board chief Deborah Hersman said at a briefing based on the plane's cockpit and flight data recorders. Three seconds later came a warning that the plane was about to stall. Just 2 1/2 seconds later, the crew tried to abort the landing and go back up for another try. The air traffic controller guiding the plane heard the crash that followed almost instantly, Hersman said.
While investigators from both the U.S. and South Korea are in the early stages of an investigation that will include a weekslong examination of the wreckage and alcohol tests for the crew, the news confirmed what survivors and other witnesses had reported: a slow-moving airliner flying low to the ground.
"We are not talking about a few knots" difference between the aircraft's target landing speed of 137 knots, or 157 mph (250 kph), and how fast it was going as it came in for a landing, Hersman said.
Pilots normally try to land at the target speed, in this case 137 knots, plus an additional 5 more knots, said Bob Coffman, an American Airlines captain who has flown 777s. He said the briefing raises an important question: "Why was the plane going so slow?"
The airline said Monday in Seoul that the pilot at the controls had little experience flying that type of plane and was landing one for the first time at that airport.
Asiana spokeswoman Lee Hyomin said that Lee Gang-guk, who was at the controls, had nearly 10,000 hours flying other planes but only 43 in the 777, a plane she said he still was getting used to flying. Another pilot on the flight, Lee Jeong-min, had about 12,390 hours of flying experience, including 3,220 hours on the 777, according to the Ministry of Land, Infrastructure and Transport in South Korea. Lee was the deputy pilot, tasked with helping Lee Gang-guk get accustomed to the 777, according to Asiana Airlines.
Two other pilots were aboard, with teams rotating at the controls.
The plane's Pratt & Whitney engines were on idle and the pilots were flying under visual flight rules, Hersman said. Under visual flight procedures in the Boeing 777, a wide-body jet, the autopilot would typically have been turned off while the automatic throttle, which regulates speed, would have been on until the plane had descended to 500 feet (150 meters) in altitude, Coffman said. At that point, pilots would normally check their airspeed before switching off the autothrottle to continue a "hand fly" approach, he said.
There was no indication in the discussions between the pilots and the air traffic controllers that there were problems with the aircraft.
Survivors and rescuers said it was nothing less than astonishing that nearly everyone survived after a frightful scene of fire burning inside the fuselage, pieces of the aircraft scattered across the runway and people fleeing for their lives.
In the first comments on the crash by a crew member, cabin manager Lee Yoon-hye said that seconds before impact she felt that something was wrong.
"Right before touchdown, I felt like the plane was trying to take off. I was thinking 'what's happening?' and then I felt a bang," Lee told reporters Sunday night in San Francisco. "That bang felt harder than a normal landing. It was a very big shock. Afterward, there was another shock and the plane swayed to the right and to the left."
She said that during the evacuation, two inflatable slides that were supposed to inflate toward the outside instead inflated toward the inside of the plane, hurting two Asiana flight attendants. Pilots came to rescue the flight attendants but even after getting injured, she said that the crew did not leave the plane until after the passengers evacuated. She said she was the last one to go.
South Korea's Ministry of Land, Infrastructure and Transport said the 291 passengers included 141 Chinese, 77 South Koreans, 64 Americans, three Canadians, three Indians, one Japanese, one Vietnamese and one person from France.
The two dead passengers have been identified as students from China - 16 and 17 years old - who were scheduled to attend summer camp in California with dozens of classmates. Hospital officials said Sunday that two of the people who remained hospitalized in critical condition were paralyzed with spinal injuries, while another two showed "road rash" injuries consistent with being dragged.
Foucrault, the coroner, said one of the bodies was found on the tarmac near where the plane's tail broke off when it slammed into the runway. The other was found on the left side of the plane about 30 feet (10 meters) away from where the jetliner came to rest after it skidded down the runway. Foucrault said an autopsy he expects to be completed by Monday will involve determining whether the second girl's death was caused by injuries suffered in the crash or "a secondary incident."
He said he did not get a close enough look at the victims on Saturday to know whether they had external injuries.
The flight originated in Shanghai, China, and stopped over in Seoul, South Korea, before making the nearly 11-hour trip to San Francisco.
When the plane hit the ground, oxygen masks dropped down, said Xu Da, a product manager at an Internet company in Hangzhou, China, who was sitting with his wife and teenage son near the back of the plane. He stood up and saw sparking - perhaps from exposed electrical wires - and a gaping hole through the back of the plane where its galley was torn away along with the tail.
Xu and his family escaped through the opening. Once on the tarmac, they watched the plane catch fire, and firefighters hose it down.
In the chaotic moments after the landing, when baggage was tumbling from the overhead bins onto passengers and people all around her were screaming, Wen Zhang grabbed her 4-year-old son, who hit the seat in front of him and broke his leg.
Spotting a hole at the back of the jumbo jet where the bathroom had been, she carried her boy to safety.
"I had no time to be scared," she said.
Nearby, people who escaped were dousing themselves with water from the bay, possibly to cool burn injuries, authorities said.
By the time the flames were out, much of the top of the fuselage had burned away. The tail section was gone, with pieces of it scattered across the beginning of the runway. One engine was gone, and the other was no longer on the wing.
Associated Press writers Joan Lowy in Washington D.C., Jason Dearen, Terry Collins, Terry Chea, Lisa Leff and Sudhin Thanawala in San Francisco, David Koenig in Dallas, Louise Watt in Beijing and Hyung-jin Kim in Seoul contributed to this report.