BUFFALO, N.Y. (AP) -- Investigators began gathering pieces of the incinerated wreckage of a commuter airliner early Saturday in search of clues to the cause of the fiery crash that killed 50 people.
Workers also had begun the somber task of removing the remains of the victims from the crash site - a suburban house.
Recovery could take several days, said Steve Chealander, spokesman for the National Transportation Safety Board. "We're very sensitive to the families," he said.
Investigators have been examining instrument data and have listened to the last words of the pilot and co-pilot of Flight 3407 in an effort to determine whether ice on the plane's wings caused the crash.
Officials say the crew of the Continental Connection flight remarked upon significant ice buildup on the wings and windshield shortly before the aircraft pitched violently and slammed into the house Thursday night.
Ice on the wings can interfere catastrophically with an aircraft's handling and has been blamed for a number of major air disasters over the years, but officials said they had drawn no conclusions as to the cause of this crash.
Chealander said early Saturday that the icing noted by the pilot of Flight 3407 is just one of several things investigators are looking at.
Investigators will probably stay in Buffalo for another week before shipping plane parts for study, with a full report not likely for another year, Chealander said.
The NTSB has been pressing for more regulations to improve deicing, he said.
"We don't like the progress that's taken place right now," Chealander said. "It's something that requires constant focus."
The NTSB had made recommendations "for several years," he said.
The aircraft, bound to Buffalo from Newark, N.J., went down in light snow and mist - ideal icing conditions - about six miles short of the Buffalo airport, plunging nose-first through the roof of the house in the suburb of Clarence.
All 44 passengers, four crew members, an off-duty pilot and one person on the ground were killed. Two others escaped from the home, which was engulfed in a fireball that burned for hours, making it too hot to begin removing the bodies until around nightfall Friday.
Families of the victims remained secluded in a hotel Saturday, and police turned reporters away.
Investigators pulled the "black box" flight recorders from the incinerated wreckage, sent them to Washington and immediately began analyzing the data. The full analysis will take weeks, Chealander said.
It was the nation's first deadly crash of a commercial airliner in 2 1/2 years.
One of the survivors from the house, Karen Wielinski, 57, told WBEN-AM that she was watching TV when she heard a noise. She said her daughter, 22-year-old Jill, who also survived, was watching TV elsewhere in the house.
"When the ceiling first fell down, I think the first thing I said to myself was, 'Is this real? Is this reality? Was I dreaming something?'" she told the station. "I didn't think I was going to get out of there. I thought, this is it."
She escaped with only a fractured collar bone, while her daughter suffered scratches to her feet.
Her husband, Doug, had gone up to bed and was in the middle of the house, where the plane hit.
"He was a good person, loved his family," Wielinski said.
Among the passengers killed was a woman whose husband died in the World Trade Center attacks of Sept. 11; one of the world's leading experts on the Rwandan genocide; and two musicians who played with trumpeter Chuck Mangione.
Chealander said Friday that the crew of the twin-engine turboprop discussed ice buildup on the windshield and the leading edge of the wings at an altitude of around 11,000 feet as the plane was descending for a landing.
The flight data recorder indicated the plane's deicing equipment was in the "on" position, but Chealander would not say whether the equipment was functioning.
The landing gear was lowered one minute before the end of the flight at an altitude of more than 2,000 feet, and 20 seconds later the wing flaps were set to slow the plane down, after which the aircraft went through "severe pitch and roll," Chealander said.
The crew raised the landing gear at the last moment, just before the recording ran out. No mayday call came from the pilot.
"Icing, if a significant buildup, is an aerodynamic impediment, if you will," Chealander said. "Airplanes are built with wings that are shaped a certain way. If you have too much ice, the shape of the wing can change requiring different airspeeds."
But he refused to draw any conclusions from the data, and cautioned: "We are not ruling anything in or anything out at this time."
Witnesses heard the plane sputtering before it plunged through the roof of the house.
"I saw a glow in the sky and I ran to get my husband," said Michelle Winer, 46. "He thought I was crazy, and then there was a huge explosion. You heard it and felt it."
After the crash, at least two pilots were heard on air traffic control circuits saying they had been picking up ice on their wings.
The 74-seat Q400 Bombardier aircraft, in the Dash 8 family of planes, was operated by Colgan Air, based in Manassas, Va. Colgan's parent company, Pinnacle Airlines of Memphis, Tenn., said the plane was new and had a clean safety record.
The pilot, Capt. Marvin Renslow, had been with the airline for nearly 3 1/2 years and had more than 3,000 hours of flying experience with Colgan, which is nearly the maximum a pilot can fly over that period of time under government regulations.
The last fatal U.S. crash of a commercial airliner was on Aug. 27, 2006, when a Comair airliner took off from a runway in Lexington, Ky., that was too short. The crash killed 49 people.
Contributing to this report were Associated Press writers John Wawrow, Ramit Plushnick-Masti and Larry Neumeister in Clarence, and Cristian Salazar, Jennifer Peltz and the AP News Research Center in New York.