(CNN) -- Two people died after a Boeing 777 from South Korea crashed Saturday upon landing at San Francisco's airport, sending up a huge fireball, shedding its tail and spinning before screeching to a stop.
Asiana Airlines Flight 214 left Seoul's Incheon International Airport earlier Saturday, according to FlightAware, a website that offers tracking services for private and commercial air traffic. An airline spokesman in Seoul told CNN that 291 passengers and 16 staff members were aboard when it crashed around 11:30 a.m. (2:30 p.m. ET).
WATCH: Dramatic, raw footage of crash as it happened
Two people have died, San Francisco Fire Chief Joanne Hayes-White said.
She said around 4:10 p.m that more than 60 people were unaccounted for. But about 1½ hours later, Assistant Deputy Chief Dale Carnes from the same San Francisco fire department said authorities had accounted for 306 people -- leaving just one person who still was not.
Local hospitals have treated 181 passengers and crew, 49 of whom were in what Carnes described as "serious" condition. Another 123 people now in the airport terminals were "uninjured," he said.
Nine Bay Area hospitals are treating patients, Hayes-White had said.
Air traffic control audio -- between the airport's tower and Flight 214 crew members -- suggested that those on the ground knew there was some sort of problem, promising that "emergency vehicles are responding."
"We have everyone on their way," the air traffic controller said, according to LiveATC.net, a website that provides air traffic control audio.
One of those on the flight, Elliott Stone, told CNN that he thought the plane was approaching "a little high (then came) down a little sharp.
"All of a sudden, boom, the back end just hit and flies up into the air and everyone's head goes up the ceiling," said Stone, who added that he ended up jumping out the plane without using the stairs or an evacuation slide.
Anthony Castorani, who witnessed the landing from a nearby hotel, said the plane touch the ground then noticed a large plume of smoke.
"You heard a pop and you immediately saw a large, brief fireball that came from underneath the aircraft," he told CNN.
Kristina Stapchuck saw the dramatic scene unfold from her seat on a plane on the airport tarmac. Soon after Flight 214 touched down, "it looked like the tires slipped a little bit and it rocked back," she told CNN.
Parts of the plane began to break off as it rocked and then began to spin.
"It all happened so suddenly," Stapchuck told CNN.
A photo provided to CNN by Eunice Bird Rah -- and shot by her father, who was a passenger on the plane -- shows flames and smoke bursting out of many of the aircraft's windows.
Rah's father knew something bad was coming, he told his daughter, telling her that the pilot appeared to try to raise the plane at the last minute. Rah said her father "is doing fine, thank God," but noted that others appeared to be hurt.
Said Rah: "It's heartbreaking."
Video taken soon after the crash and posted on YouTube showed dark gray smoke rising from the plane, which appeared to be upright. That smoke later became white, even as fire crews continued to douse the plane.
CNN iReporter Timothy Clark was on an eighth-floor balcony of a nearby hotel when he heard the noise and saw a "dust cloud."
"Then people running from the plane, then flames," Clark said.
A photograph posted to Twitter shows what appear to be passengers walking off the plane, some of them toting bags, as smoke rises from the other side.
"I just crash landed at SFO," read the accompanying message from David Eun. "Tail ripped off. Most everyone seems fine. I'm ok. Surreal..."
The top of the aircraft was charred and, in spots, gone entirely, according to video from CNN affiliate KTVU. The plane was on its belly, with no landing gear evident and the rear tail of the plane gone.
Debris settled from the water's edge, along San Francisco Bay, up to where the plane eventually came to a stop.
Fire trucks were on site; first responders could be seen walking outside the aircraft.
Evacuation slides could be seen extending from one side of the aircraft, from which there was no apparent smoke.
According to Asiana Airlines, 141 of the passengers who were aboard Flight 214 are Chinese, 77 are South Korean and 61 are American.
Sheryl Sandberg, Facebook's chief operating officer and author of the book "Lean In," was supposed to be one of them, she wrote on her Facebook page. But she'd switched instead to a United flight, arriving about 20 minutes before the Asiana flight crashed.
The Bay Area airport was closed to incoming and departing traffic after the crash, the Federal Aviation Administration said on its website, adding that the time when it's expected to reopen is unknown.
At one point flights destined for San Francisco's airport -- known by its call letters, SFO -- were diverted to airports in Oakland, Sacramento, San Jose and Los Angeles, said Zamora.
In an official tweet around 3:30 p.m., San Francisco International Airport said that two of its runways had reopened.
The airport, located 12 miles south of downtown San Francisco, is California's second busiest, behind LAX.
There were a few clouds in the sky around the time of the crash, and temperatures were about 65 degrees, according to the National Weather Service. Winds were about 8 miles per hour.
Members of South Korea's Aviation and Railway Accident Investigation Board will travel to San Francisco, that agency said. They'll be joined by members of the United States' National Transportation Safety Board, which is sending a "go team" led by chairwoman Deborah Hersman to investigate the crash.
"We have not determined what the focus of this investigation is yet," Hersman said shortly before leaving Washington for San Francisco. "Everything is on the table at this point."
There are no signs of terrorism related to the crash, a national security official told CNN. President Barack Obama was at Camp David when he learned about the crash, a senior White House official said.
Asiana Airlines -- one of South Korea's two major airlines, the other being Korean Air -- is also investigating the cause of the crash, a company spokesman told CNN.
The airline received the plane involved in the incident in 2006, according to the Aviation Safety Network. The aircraft has two Pratt & Whitney engines, it said.
Flying to 23 other countries, the 25-year-old Asiana operates many of its flights out of Incheon International Airport, which is the largest airport in South Korea and considered among the busiest in the world.
According to information on Asiana Airlines' website, the company has 12 Boeing 777 planes. The airliners have a seating capacity of between 246 and 300 people and had a cruising speed of 555 mph (894 kph).
See more on this story on local CNN affiliates KGO, KRON, KPIX and KTVU.
CNN's Mike M. Ahlers, Chelsea J. Carter, Rande Iaboni, K.J. Kwon, Kyung Lah, John King and Janet DiGiacomo contributed to this report.
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