The commuter plane was approaching a runway at Buffalo Niagara International Airport when its safety systems warned pilot Capt. Marvin Renslow that the plane was perilously close to losing lift and falling from the sky. The stick automatically pushed forward, the plane's nose dropping in a last-minute corrective measure before it belly-flopped onto a house in a fireball — landing with its nose pointed away from the runway.

But National Transportation Safety Board officials still wouldn't say Saturday whether ice brought down the plane, deepening the mystery of what caused the flight from Newark, N.J., to crash about six miles shy of the runway Thursday, killing all 49 people aboard and one on the ground.

The plane didn't nose-dive into the house, as initially reported by some witnesses, said Steve Chealander, an NTSB member.

Cleared to land on a runway pointing to the southwest, the plane crashed in light snow and mist with its nose pointed northeast, according to Chealander.

"We didn't hear anything on the (cockpit voice recorder) or any maydays or any warnings," he said. "It was just a sudden catastrophic event that took place and then 30 seconds later, they impacted the ground."

It will take as many as four days to remove human remains from the site, which he called an "excavation."

"Keep in mind, there's an airplane that fell on top of a house, and they're now intermingled," he said.

A "stick shaker" and "stick pusher" mechanism had activated to warn Renslow that the plane was about to lose aerodynamic lift, a condition called a stall. When the "stick pusher" engaged, it would have pointed the nose of the plane toward the ground to try to increase lift.

Crash investigators picked through incinerated wreckage Saturday, gathering evidence to determine what brought down the plane. Icing on the aircraft is suspected to have played a role, but officials have stopped short of calling that the cause.

Chealander said indicator lights showed that deicing equipment on the tail, wings and propeller appeared to be working and that investigators who examined both engines said it appears they were working normally at the time of the crash.

Experts were analyzing data from the black boxes, including statements by crew members about a buildup of ice on the wings and windshield of the plane, Chealander said.

If ice is a problem in flight, guidelines from the Aircraft Owners and Pilots Association Air Safety Foundation say pilots can take a number of steps, including changing speed, pulling the nose up or down, or trying a 180-degree turn.

On Friday, U.S. Sen. Robert Menendez, D-N.J., said Transportation Secretary Ray LaHood had told him he believes the aircraft made a 180-degree turn at 5,000 feet.

But there could be other explanations for why the plane was facing the wrong way.

Chealander said the NTSB would use data on the black boxes to determine whether the plane was in a flat spin before it crashed. Flight data indicated "severe" pitching and rolling before impact, so the violent nature of the crash also could have turned the aircraft around.

Other aircraft in the area Thursday night told air traffic controllers they also experienced icing around the time that the plane went down.

Icing is one of several elements being examined by investigators, Chealander said, adding that a full report will probably take a year.

One aspect of the investigation will focus on the crew, including how they were trained and whether they had enough time to rest between flights. Other investigators focused on the weather, the mechanics of the plane and whether the engine, wings and various mechanics of the plane operated as they were designed.

Victims' family members, who were briefed about the findings Saturday, have been asked to provide DNA samples and dental records to help identify remains, according to Anthony Billitier, the county health commissioner.

Many in this Buffalo suburb are still thinking about the crash.

"You can't stop thinking about it," said neighbor Donna Truman, 57, who lives near the house where the plane landed. "A plane came down three houses away. As much as you feel bad for the victims and their families, you're thankful for your life."

___

Associated Press writers Carolyn Thompson, William Kates, Larry Neumeister, John Wawrow and Ramit Masti contributed to this report.