Probe into fatal San Francisco jet crash begins

US investigators were combing through the wreckage of a Asiana Airlines Boeing 777 passenger jet in San Francisco on Sunday, trying to determine why it crashed before the runway, killing two people and injuring 182 others.

The crash sheared off the plane's landing gear and ripped the tail off the fuselage. Large portions of the plane's body were burned out in a massive fire that then erupted.

But National Transportation Safety Board chief Deborah Hersman said much of the destruction was not visible in news pictures and video footage.

"What you can't see is the damage internally. And that is really striking. I think when we look at this accident, we're thankful that we didn't have more fatalities and serious injuries and we have so many survivors," Hersman told CNN's "State of the Union."

Flight 214 originated in Shanghai, and had 307 people on board -- 291 passengers and 16 crew -- after it stopped to pick up passengers in Seoul. The aircraft apparently clipped a seawall at the water's edge short of the airport runway before smashing hitting the ground hard.

The two dead were both teenage Chinese girls, South Korea's transport ministry said. Many of the injured were still in critical condition or unconscious, the San Francisco General Hospital said in a press briefing.

Doctors saw "large amounts of abdominal injuries, a huge amount of spine fracture, some of which include paralysis, and head trauma and multiple type of orthopedic injuries," Margaret Knudson, interim surgery chief at the hospital, told reporters.

Some 15 or 16 had yet to regain consciousness, she said, adding that "some of our patients have been operated on twice already, and there's going to be many many more surgeries to come still."

Other patients had been sent to different area hospitals.

Hersman said on ABC that her investigation team arrived overnight and "have obtained the cockpit voice recorder and the flight data recorder," which were being analyzed in Washington.

They also plan to talk to the pilot "in the coming days," to understand what went wrong, she said, on ABC's "This Week."

Part of the landing assistance equipment at the airport was out of service for that runway, but Hersman said that should not have created a dangerous situation.

"There are a number of other tools available to the pilots, some less sophisticated, like the lights, precision approach lights," she told CNN, as well as "some things that are more technologically advanced, (like) things on the airplane that can give you GPS information."

But she said, with or without the instruments, the pilot's expertise is crucial.

"So for them to be able to assess what's happening and make the right inputs to make sure they're in a safe situation -- that's what we expect from pilots," she told CNN.

Yoon Young-Doo, the CEO of the Seoul-based Asiana Airlines, had said earlier that "currently we understand that there are no engine or mechanical problems" with the plane bought in 2006.

It was flown by experienced pilots, and there was no emergency warning ahead of the crash, Yoon said, adding "our pilots strictly comply with aviation rules."

"Please accept my deepest apology," the CEO said, bowing in front of TV cameras at a press conference in Seoul.

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

Aboard the flight were 141 Chinese nationals, 77 South Koreans, 64 Americans, one Japanese, three Indians, three Canadians, one French, one Vietnamese, three others of unidentified nationality. There were also 16 crew members, according to Asiana.

San Francisco International Airport was closed after the crash but operating normally Sunday.

In total, 123 people aboard the flight escaped unharmed, US officials said.

Survivor Elliott Stone told CNN that as the jet came in to land, it appeared to have "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."

"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."

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."

South Korean President Park Geun-Hye offered his "deepest condolences to the victims and their relatives," and promised that all government agencies concerned "will join forces to provide all necessary assistance and resources to deal with the disaster."

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.