But National Transportation Safety Board member John Hammerschmidt said it was possible that the switches and levers were flipped, pulled or twisted by the force of the crash, rather than by the pilot or co-pilot of Comair Flight 3272 from Cincinnati.
And all damage to the right engine appears to have been caused by the crash impact, he said. On Saturday, Hammerschmidt said preliminary findings were that both engines appeared to have been rotating when the plane hit the ground.
There were no signs of fire in the right engine, he said, and the switches meant to shut off the left engine were found in the off position.
Hammerschmidt also said a preliminary reading of the flight data recorder showed that the plane was making a stable, 30-degree banking left turn on autopilot for three seconds, and then over the next eight seconds the turn increased to 40 degrees.
At that point, the autopilot was shut off and the plane crashed 17 seconds later.
Still unclear was what "event" led to the plane's roll and nosedive into a field 18 miles from Detroit Metropolitan Airport. Hammerschmidt had said Saturday that the flight appeared normal until the "event."
"The 'event' was termed an 'event' by the people who were listening to our cockpit voice recorders. What they meant precisely by an 'event' is still unclear," he said yesterday.
"When we said 'event' ... we meant that something occurred. It could not be defined. It could not be explained. It was sort of a puzzle."
While the investigation continued yesterday, about 200 of the victims' relatives visited the crash site and a memorial made of hay bales.
About 150 yards from the craters dug by the plane's nosedive are a dozen square hay bales surrounding a blue sign with white lettering:
"In memory of passengers and crew of Comair flight 3272 from the community of Monroe County and southeast Michigan."
And at Immaculate Heart of Mary Motherhouse Chapel in Monroe, about 1,000 people attended a memorial service for the crash victims. The Rev. David Campbell, a chaplain at Mercy Memorial Hospital, told relatives, friends and community members that their lives would be intertwined forever.
"Your lives have touched ours," he said. "None of us will ever be the same."
About 30 investigators combed through the site yesterday, putting debris and human remains in bags. The crews were still focusing on recovering the remains, according to a news pool established by the NTSB.
In yesterday's 9-degree temperatures, searchers warmed themselves in a tent near the crater.
Two large pieces of the plane - a cargo door and a piece of the skin of the airplane - had landed about 100 yards from the scorched area near the 30-foot-wide crater left by the burning wreckage.
Hammerschmidt said the pilot and co-pilot of flight 3272, a twin-engine turboprop Embraer 120, reported nothing unusual during the flight, air traffic controllers said nothing seemed amiss, and crew who had flown the plane earlier in the day reported that all was well.
"The cockpit voice recorder indicates an uneventful, routine, orderly, businesslike flight from Cincinnati into the Detroit area," Hammerschmidt said.
The only other evidence of trouble during the plane's final moments so far have come from eyewitnesses, who saw the plane spinning or turning, stabilize, then plummet to earth.
One witness told investigators that the plane had spun over to its right several times. Two others said the plane's wings had been rocking before the crash.
"They all indicated that the airplane stabilized, then the nose of the aircraft abruptly pitched and descended vertically to the ground," Hammerschmidt said.
Before flight 3272 took off, there had been two warnings about "moderate, occasional, severe turbulence," Hammerschmidt said.
Shortly after the crash, a DC-3 pilot in the area made a report of moderate, mixed icing at 5,000 feet, he said. Ice on the wings can change the shape of the surfaces that lift the plane, causing a loss of control.
Investigators say the crew was aware of the weather. The de-icing systems on flight 3272 apparently had been turned on and working, according to the cockpit voice recorder. But investigators will do more tests to see if they were working when the plane crashed.
The plane was de-iced before leaving Cincinnati, Hammerschmidt said.
NTSB officials have refused to offer analysis of the evidence so far. Hammerschmidt didn't know when more analysis of the voice and flight data recorders would be completed.
At a temporary morgue in the Monroe County airport, 125 people were working in two shifts from 6 a.m. until midnight to identify the remains, a process that the chief county medical examiner said could take several days.
"We're approaching it with as much dispatch as we can to identify the dead and comfort the living," Dr. David Lieberman said.