Media playback is unsupported on your device Media caption New video of San Francisco plane crash

Pilots of the plane that crashed at San Francisco airport on Saturday tried to abort the landing seconds before touching down, US investigators say.

Initial inquiries suggested the Asiana plane was flying "significantly below" its target speed on approach.

And the Korean airline revealed that the pilot was landing a Boeing 777 at San Francisco for the first time.

Two Chinese teenagers died and more than 180 people were injured when the plane hit the seawall.

'Standard practice'

Sixty of the passengers on board the flight from Seoul, including the two girls who died, were Chinese schoolchildren on their way to summer camp.

Image copyright AP Image caption Ye Mengyuan (left) and Wang Linjia were described as close friends

Chinese state media named the two as Ye Mengyuan and Wang Linjia, both 16, who were classmates at a school in eastern Zhejiang Province.

Both girls were pronounced dead at the airport. A coroner is trying to determine if one of the victims was run over and killed by an emergency vehicle.

Two fire chiefs raised that possibility at a news conference on Monday.

Their families, as well as relatives of the injured, are travelling to San Francisco.

More than 30 people remained in hospital late on Sunday.

Medical officials said eight were listed in critical condition, including two with paralysis from spinal injuries.

Asiana said 141 of the 291 passengers were Chinese, 77 were Korean and 61 were Americans.

At a news conference on Sunday, National Transportation Safety Board (NTSB) chief Deborah Hersman said the aircraft's speed was below the planned 137 knots (158mph; 254km/h) as it approached the runway.

"We are not talking about a few knots here or there. We're talking about a significant amount of speed below 137," she said.

Image copyright Reuters Image caption Smoke billows from the burning plane after it crash-landed on San Francisco International Airport's Runway 28L Image copyright Getty Images Image caption More than 300 people were on Asiana Airlines Flight 214, which had taken off from South Korea's capital, Seoul Image copyright Reuters Image caption Firefighters and rescue teams were quickly at the scene Image copyright AP Image caption The tail fin broke off during the crash and could be seen lying on its side apart from the main wreckage Image copyright AP Image caption Fire engines could be seen spraying a white fire retardant into gaping holes in the wrecked plane's roof previous slide next slide

She said the pilots had tried to speed up, before trying to abort the landing less than two seconds before touching down.

My [eight-year-old] son told me, 'the plane will fall down, it's too close to the sea.' I told him, 'no, baby, it's OK, we'll be fine'

Ms Hersman stressed that it was too early to speculate on precise causes for the accident.

The airline said mechanical failure did not appear to have been a factor.

Late on Sunday, Asiana released more details about the pilot, Lee Kang-kuk.

They said he had only 43 flying hours in a Boeing 777, and was assisted by another more experienced pilot as he landed the aircraft.

The airline insisted such in-flight supervision was standard practice within the aviation industry.

Meanwhile, US officials confirmed that a navigation system helping pilots make safe descents had been turned off for maintenance since June.

The Glide Path is used for landings in bad weather conditions, but it was clear and sunny when the Asiana Airlines aircraft crashed.

Inflatable slide injuries

The Boeing 777 has a good safety record, and this is thought to be the first fatal crash.

The only previous notable crash occurred when a British Airways plane landed short of the runway at London's Heathrow Airport in 2008.

Boeing 777 fact sheet Twin-engine jet launched in June 1995

One of the world's most popular long-distance planes

Seats between 300 and 380 passengers

Has flown around five million flights

Often used for non-stop flights of 16 hours or more

Prior to Asiana crash, only one fatal accident when a crew member died during a re-fuelling fire at Denver International Airport in September 2001

Footage of the scene in San Francisco on Saturday showed debris strewn on the runway and smoke pouring from the jet, as fire crews sprayed a white fire retardant into gaping holes in the aircraft's roof.

One engine and the tail fin were broken away from the main wreckage.

Cabin manager Lee Yoon-hye told reporters that during the evacuation, two slides had inflated toward the inside of the plane, instead of outside, hurting two flight attendants.

Passenger Ben Levy said the accident "happened in a flash" and there was "chaos, disbelief, screaming".

Nevertheless, people "calmed down pretty quickly", he added, and evacuated the plane without a stampede.

Another passenger, David Eun, tweeted a picture of people going down the plane's emergency inflatable slides and wrote: "I just crash landed at SFO. Tail ripped off. Most everyone seems fine. I'm ok. Surreal."

A Chinese passenger, Fei Xiong, wearing a neck brace after being injured during the crash landing, told a San Francisco news conference her eight-year-old had noticed something was wrong during the plane's descent.

"My son told me, 'the plane will fall down, it's too close to the sea,'" she said. "I told him, 'no, baby, it's OK, we'll be fine.' And then the plane just fell down."