An Asiana Airlines Boeing 777 passenger jet crashed and burst into flames Saturday as it landed short of the runway at San Francisco International Airport, killing two people and injuring 182 others.

Flight 214 had 307 people on board -- 291 passengers and 16 crew -- when it left Seoul. The aircraft apparently struck a rocky area at the water's edge short of the runway at the airport, a major international hub especially for flights to and from Asia.

"It is incredible and very lucky that we have so many survivors. But there are still many that are critically injured," said San Francisco Mayor Edwin Lee, who sent condolences to the families of those killed and hurt.

The plane's tail "hit the runway and the aircraft veered to the left out of the runway," South Korea's transportation ministry said in a statement Sunday from Seoul.

Pictures showed the tail detached from the fuselage, and the landing gear had also sheared off.

The airport was closed immediately after the crash, but two runways later reopened. Some flights were diverted to Los Angeles.

Among those on board were 77 Koreans, 141 Chinese, 61 US citizens, and one Japanese national, Asiana said in a statement.

In Seoul, Asiana Airlines CEO Yoon Young-Doo said that there was nothing wrong with the airplane.

"We purchased this airplane in March 2006... currently we understand that there are no engine or mechanical problems," he said at a press conference, adding that the two people killed were Chinese nationals.

San Francisco General Hospital said it was treating 34 patients, five of them in critical condition. Other patients had been taken to different hospitals in the area.

In total, 123 people aboard the flight were uninjured, US officials said.

Survivor Elliott Stone told CNN that as it came in to land, it appeared the plane "sped up, like the pilot knew he was short."

"And then the back end just hit and flies up in the air and everybody's head goes up to the ceiling."

Video footage showed the jet on its belly surrounded by at least six fire engines that sprayed white foam on the wreckage. Debris was scattered on the runway and in the surrounding area.

"It looked normal at first... the wheels were down," an unidentified man who witnessed the crash told CNN. "It just hit (the seawall) like that and the whole thing just collapsed immediately.

"It just pancaked immediately. The wings caught on the tarmac."

A four-member South Korean government team was also heading to inspect the site of the accident, officials in Seoul said.

One dramatic photo tweeted by a survivor showed people streaming out of the jet following the crash-landing. An inflatable slide was at the front entrance. Other emergency exits also appeared to have been used.

"I just crash landed at SFO. Tail ripped off. Most everyone seems fine. I'm ok," the passenger, David Eun, wrote on Twitter.

But another photo from above showed a more distressing scene, with most of the roof of the plane missing and the cabin seating area charred by fire. The aircraft's wings were still attached.

"I saw some passengers bleeding and being loaded onto an ambulance," another passenger, Chun Ki-Wan, told YTN TV in Seoul.

"Everything seemed to be normal before it crash-landed."

Stone said he feared for the flight crew seated in the back of the plane, which took off in Shanghai, stopped in Seoul before heading to the United States.

"They were sitting in the back end and got hammered because we landed short. And then they all fell out and it was just the most terrible thing I've seen," he said.

Facebook Chief Operating Officer Sheryl Sandberg was supposed to be on the flight with her family and three colleagues, but switched to a United flight and arrived in San Francisco some 20 minutes before the Asiana crash.

"Serious moment to give thanks," she wrote on her own Facebook page.

The White House said President Barack Obama had been briefed on the incident, noting: "His thoughts and prayers go out to the families who lost a loved one and all those affected by the crash."

Asiana is based in Seoul. The twin-engine 777 aircraft is one of the world's most popular long-distance planes, often used for flights of 12 hours or more, from one continent to another.

It was the first fatal crash involving an Asiana passenger plane since June 1993, when a Boeing 737 operated by the carrier crashed into a mountain in South Korea, killing 68.

The US Federal Bureau of Investigation (FBI) said there was no indication that terrorism was to blame for the crash.

In Washington, National Transportation Safety Board experts flew west to investigate the crash, while the heads of the US Department of Transportation and the Federal Aviation Administration issued a joint statement thanking the first responders. "Our thoughts and prayers go out to the passengers and crew of Asiana Flight 214 and their families," the statement read.