BUFFALO, N.Y. —The commuter plane that crashed near Buffalo was on autopilot when it went down in icy weather, indicating that the pilot may have violated federal safety recommendations and the airline’s own policy for flying in such conditions, a federal official said today.

Steve Chealander, a National Transportation Safety Board member, said the company that operated the flight recommends pilots fly manually in icy conditions. Pilots are required to do so in severe ice.

“You may be able in a manual mode to sense something sooner than the autopilot can sense it,” Chealander said, explaining why the NTSB also recommends that pilots disengage the autopilot in icy conditions.

The preliminary investigation indicates the autopilot was still on when the plane crashed, he said. That has not been confirmed by information from the plane’s flight data recorder.

The pilots of Continental Flight 3407 discussed “significant” ice buildup on their wings and windshield just before crashing into a home Thursday night in a suburban neighborhood near the Buffalo airport. Forty-nine people aboard the plane were killed, as well as the homeowner.

The flight was run by Colgan Air, which operates a fleet of 51 regional turboprops for Continental Connection, United Express and US Airways Express.

In a December safety alert issued by the NTSB, the agency said pilots in icy conditions should turn off or limit the use of the autopilot to better “feel” changes in the handling qualities of the airplane.

Chealander also said Colgan, like most airline companies, had begun following NTSB recommendations that pilots use deicing systems as soon as they enter conditions that might lead to icing.

He said it was not yet clear exactly when the pilot on Flight 3407 turned on the plane’s advanced deicing system.

Authorities have recovered the remains of 15 people from the wreckage as crews raced to finish their work before a storm arrives later in the week.

Erie County Executive Chris Collins said recovery efforts intensified after the arrival of additional federal workers. A forecast of snow for Wednesday added to the urgency.

The storm could hamper recovery efforts, but “the investigation will continue snow, rain or shine,” said David Bissonette, the town’s emergency coordinator.

Recovery crews could need as much as four days to remove the remains from the site. Chealander described the efforts as an “excavation.”

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

DNA and dental records will be used to identify the remains, he said.

Once all the remains are recovered, the focus will turn to removing wreckage of the 74-seat aircraft from the residential neighborhood where it went down Thursday night near the end of a flight from Newark, N.J.

About 150 people were working at the site. The blue tail of the plane still stuck out from a mound of black ash and rubble.

The turboprop, flying through light snow and mist, crashed belly first into the house, with the aircraft’s nose pointed away from the airport.

Investigators did not offer an explanation, but the orientation raised the possibility that the pilot was fighting an icy airplane. Possible explanations are that the aircraft was spinning or flipped upon impact.

According to the flight data recorder, the plane’s safety systems warned the pilot that the aircraft was perilously close to losing lift and plummeting from the sky.

Moments before the crash, a “stick shaker” and “stick pusher” mechanism had activated to warn the pilot 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.

Indicator lights showed that deicing equipment on the tail, wings and propeller appeared to be working, Chealander said.

Investigators who examined both engines said it appears they were working normally at the time of the crash, too.

Experts were also analyzing data from the flight data recorder and the cockpit voice recorder, including statements by crew members describing a buildup of ice on the wings and windshield, Chealander said.

The NTSB planned to use that data to determine whether the plane was in a flat spin before it crashed. Flight data indicated “severe” pitching and rolling before impact.

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, their training and whether they had enough time to rest between flights. Other investigators will review the weather and the mechanics of the plane.