WASHINGTON ( CNN ) -- The crew of a commuter plane that crashed outside Buffalo , New York , in February may have responded improperly to signs the plane was stalling , according to details of the investigation released Wednesday . Only a few pieces of the Continental Connection Dash 8 turboprop were recognizable after the crash . The crew of Continental Connection Flight 3407 pulled back on the plane 's control column when it received a stall warning , pulling the plane upward , an update released by the National Transportation Safety Board revealed . That would have aggravated the situation rather than improving it , according to a veteran pilot contacted by CNN . But investigators are far from determining the exact cause of the crash , the NTSB said . And Colgan Air , the plane 's operator , urged the public not to jump to conclusions . The Bombardier Dash 8 Q400 crashed into a house about six miles from Buffalo-Niagara International Airport the night of February 12 . All 49 people on the plane and one man who was in the house were killed . The pilot and first officer discussed `` significant '' ice buildup on the aircraft 's windshield and wings before the crash , the cockpit voice recorder revealed . But in an update on the investigation , the NTSB said there is no indication that aircraft 's systems failed , or that ice had a significant impact on the plane . The NTSB said a stall warning device known as a `` stick shaker '' appears to have behaved properly , activating when the plane 's speed dropped to 130 knots ( 150 mph ) . At that point , however , `` there was a 25-pound pull force on the control column , '' pulling the plane upward , and data suggests there was a `` likely separation of the airflow over the wing '' -- meaning the plane had stalled . `` The circumstances of the crash have raised several issues that go well beyond the widely discussed matter of airframe icing , '' the NTSB 's acting chairman , Mark Rosenker , said in a statement on the findings . In general , when a stick shaker activates , pilots are taught to apply full power and maintain the plane 's altitude or lower the nose , a captain for a major airline told CNN . `` What you do n't want to do is aggravate the situation , '' said the pilot , who would not be named because he had not sought approval from his airline . `` By pulling it up without adding power , you 're aggravating the situation . '' The safety board said it intends to investigate `` stall recovery training '' among other issues at a three-day public hearing it will offer on the crash in mid-May . Doug Moss , a United Air Lines pilot and aerospace consultant , said that appears to be what the NTSB `` is really looking at . '' `` It 's easy to build a lot of experience in airline flying without ever getting close to the edges of the envelope , '' he said . In a statement issued Wednesday afternoon , Colgan Air said the NTSB data does not pinpoint a cause , and its crews `` are prepared to handle emergency situations they might face . '' `` We stand by our FAA-certified crew training programs which meet or exceed the regulatory requirements for all major airlines and include training on emergency situations , '' the Virginia-based carrier said . Colgan Air said it is `` cooperating thoroughly '' with the investigation . `` The only absolute fact is that we do not know the cause of this accident , '' it said . Information released Wednesday appears to count out one possibility that was the subject of speculation after the crash : a stall induced by ice on the aircraft 's tail . Pilots say those stalls are particularly insidious because pilots can not see the tail wings and because the recovery procedure is the opposite of a main-wing stall -- tail-wing stalls generally are overcome by raising the plane 's nose . The NTSB said that toxicology tests of the flight crew were negative for alcohol or illicit substances . The captain tested positive for diltiazem , a prescription blood pressure medication the Federal Aviation Administration had permitted him to use . At the board 's hearing in May , the NTSB will look into a number of topics , including the effect of ice on the aircraft 's performance , cold weather operations , the crew 's experience and sleep issues . The board also will investigate `` sterile cockpit rules , '' or requirements that crews discuss only aircraft issues during critical phases of flight , such as take-offs and landings . CNN 's Allan Chernoff contributed to this report .
NEW : Plane 's operator : Cause still not known ; public should n't jump to conclusions . NTSB : Crew pulled back on control column after stall warning . A pilot tells CNN that move would have aggravated the situation . All 1 aboard , plus 49 in house , were killed in May crash near New York , Buffalo .