SAN FRANCISCO (Reuters) - United States officials examined flight information recorders and began investigating the crash of an Asiana Airlines Boeing 777 that burst into flames upon landing in San Francisco, killing two young passengers and injuring more than 180 people, officials said on Sunday.
There was no immediate indication of the cause of Saturday's accident, but Asiana said mechanical failure did not appear to be a factor. The airline declined to blame either the pilot or the San Francisco control tower.
Mr Eric Weiss, a spokesman for the National Transportation Safety Board (NTSB), said the plane's "black boxes" - the cockpit voice recorder and flight data recorder - had been recovered and were being sent to Washington for analysis. The Federal Aviation Administration also was investigating.
NTSB chairman Deborah Hersman said on Sunday there was no indication of a criminal act, but it was too early to determine what went wrong.
"Everything is still on the table," she said on NBC's Meet the Press show. Witnesses said the tail of the plane, which was coming in from Seoul, appeared to hit the approach area of the runway that juts into San Francisco Bay. One witness said the plane appeared to be coming in too low and too fast.
The tail came off and the aircraft appeared to bounce violently, scattering a trail of debris before coming to rest on the tarmac.
Pictures taken by survivors showed passengers hurrying away from the wrecked plane. Thick smoke billowed from the fuselage and TV footage later showed the aircraft gutted and blackened by fire. Much of its roof was gone.
The dead were both teenage female Chinese nationals who had been seated at the rear of the aircraft, according to government officials in Seoul and Asiana.
The crash was the first fatal accident involving the Boeing 777, a popular long-range jet that has been in service since 1995. It was the first fatal commercial airline accident in the US since a regional plane operated by Colgan Air crashed in New York in 2009.
"For now, we acknowledge that there were no problems caused by the 777-200 plane or (its) engines," MR Yoon Young Doo, the president and chief executive of Asiana, told reporters on Sunday at the company headquarters on the outskirts of Seoul.
Asiana said the flight, which had originated in Shanghai, had carried 291 passengers and 16 crew members. The passengers included 141 Chinese, 77 South Koreans, 61 US citizens and one Japanese citizen, but the airline did not give the nationality of the others.
Mr Dale Carnes, assistant deputy chief of the San Francisco Fire Department, said 49 people were hospitalised with serious injuries. Another 132 suffered moderate and minor injuries.
Five people were in critical condition at San Francisco General Hospital, according to spokesman Rachael Kagan. She said a total of 52 people were treated for burns, fractures and internal injuries. Three people were in critical condition at Stanford Hospital.
San Francisco International Airport, a major West Coast hub and gateway to Asia, was shut down for several hours after the crash as scores of safety workers scoured the airfield for debris.
Survivor Benjamin Levy told a local NBC station he believed the Asiana plane had been coming in too low.
"I know the airport pretty well, so I realized the guy was a bit too low, too fast, and somehow he was not going to hit the runway on time, so he was too low... he put some gas and tried to go up again," he said in a telephone interview.
"But it was too late, so we hit the runway pretty bad, and then we started going up in the air again, and then landed again, pretty hard."
Mr Levy said he opened an emergency door and ushered people out. "We got pretty much everyone in the back section of the plane out," he said. "When we got out there was some smoke. There was no fire then. The fire came afterwards."
Photos and TV images showed that emergency chutes had been deployed from at least two of the aircraft's exits.
Ms Ying Kong of the Bay Area city of Albany, who was waiting at the airport for her brother-in-law Fawen Yan, 47, from Richmond, California, said he telephoned her after surviving the crash to say it had been "really smoky and scary".
"He feels it difficult to breathe, but he's okay," she said. "He said a lot of people had to run."
Mr Vedpal Singh, a native of India, was on board the flight along with his wife and son when the aircraft struck the landing strip.
"Your instincts take over. You don't know what's going on," said Mr Singh, who had his arm in a sling as he walked through the airport's international terminal and told reporters he had suffered a fractured collar bone.
"I'm very, very thankful to God," he said.
San Francisco Mayor Ed Lee said on Saturday night: "It is incredible and very lucky that we have so many survivors."
The Asiana flight left Seoul at 5.04pm Korean time and touched down in San Francisco at 11.28am Pacific Daylight Time, according to FlightAware, a website that tracks flights.
Asiana, South Korea's junior carrier, has had two other fatal crashes in its 25-year history.
A senior Asiana official said the pilot was Lee Jeong Min, a veteran pilot who has spent his career with the airline. He was among four pilots on the plane who rotated on two-person shifts during the 10-hour flight, the official said.
Boeing expressed concern for those on board and said it will provide technical assistance to the NTSB investigation.
A San Francisco airport spokesman said that a component of the facility's instrument landing system that tracks an incoming airplane's glide path was not working on Saturday.
Pilots and air safety experts said the glide path technology was far from essential for a safe landing in good weather.
A British Airways 777-200ER crash landed a few yards short of a runway at London's Heathrow Airport in 2008. All on board survived. Investigators blamed the crash on fuel blockages caused by ice particles formed during the long flight from Beijing - a finding that led to changes in the design of the Rolls-Royce engines used on some 777s.
The Asiana 777-200ER that crashed in San Francisco on Saturday was powered by engines from Pratt & Whitney, a subsidiary of United Technologies.