THE crew of the commuter plane that crashed into a suburban Buffalo, New York, house, killing all 49 people aboard and one person on the ground, noticed significant ice buildup on the wings and windshield just before the aircraft began pitching and rolling violently, investigators said yesterday.

Officials stopped short of saying the ice buildup caused Thursday night's crash and stressed that nothing has been ruled out. But 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.

Continental Connection Flight 3407, bound from Newark, New Jersey, went down in light snow and mist -- an ideal conditions for ice to form -- about 9 kilometers short of the Buffalo airport, plunging nose-first through the roof of a 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 raging fireball that climbed higher than the treetops and burned for hours, making it too hot to begin removing the bodies until around nightfall yesterday.

Among the passengers killed was a woman whose husband died in the World Trade Center attacks of September 11.

It was the first deadly crash of a commercial airliner in the United States in 2 1/2 years.

One of the survivors from the house, Karen Wielinski, 57, told WBEN-AM that she was watching TV in the family room when she heard a noise. She said her daughter, 22-year-old Jill, who also survived, was watching TV in another part of the house.

"Planes do go over our house, but this one just sounded really different, louder, and I thought to myself, `If that's a plane, it's going to hit something,'" she told the station. "The next thing I knew the ceiling was on me."

She said she and her daughter escaped in their socks.

"I was panicking a little but trying to stay cool," she said. "I happened to notice a little light on the right of me. I shouted first in case anybody was out there. Then I just kind of pushed what was on top of me off and crawled out the hole. ... The back of the house was gone, the fire had started. I could see the wing of the plane."

She said she hadn't been told the fate of her husband, Doug, but added: "He was a good person, loved his family."

Investigators pulled the black box recorders from the wreckage, sent them to Washington and immediately began analyzing the flight data and listening to the cockpit conversations.

Steve Chealander, a spokesman for the National Transportation Safety Board, said at an afternoon news conference that the crew of the twin-engine turboprop discussed "significant ice buildup" on the windshield and the leading edge of the wings at an altitude of around 3,352 meters as the plane was coming in for a landing.

The flight data recorder indicated the plane's de-icing 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 600 meters, 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.

Doug Hartmayer, a spokesman for Niagara Frontier Transportation Authority, which runs the Buffalo airport, said: "The plane simply dropped off the radar screen."

"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 squarely through the roof of the house, its tail section visible through the flames.

"The whole sky was lit up orange," said Bob Dworak, who lives less than a mile away. "There was a big bang, and the house shook." He added: "It looked like the house just got destroyed the instant it got hit."

William Voss, a former official of the Federal Aviation Administration and current president of the Flight Safety Foundation, a nonprofit advocacy group, said the plane's near vertical drop suggests that ice or a mechanical failure, such as wing flaps deploying asymmetrically or the two engines putting out different thrust, caused the crash.

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, Virginia. Colgan's parent company, Pinnacle Airlines of Memphis, Tennessee, 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.

Flight 3407 is the first fatal crash of a commercial airliner in the United States since August 27, 2006, when 49 people were killed after a Comair jetliner mistakenly took off from a Lexington, Kentucky, runway that was too short.

In general, smaller planes like the Dash 8, which uses a system of pneumatic de-icing boots, are more susceptible to ice buildup than larger commuter planes that use a system to warm the wings. The boots, a rubber membrane stretched over the surface, are filled with compressed air to crack any ice that builds up.

A similar turboprop jet crash 15 years ago in Indiana was caused by ice, and after that the NTSB recommended more aggressively using pneumatic de-icing boots. But the FAA has not adopted the recommendation. It remains on the NTSB's list of most-wanted safety improvements.