CLARENCE CENTER, New York (CNN) -- Recovering all the bodies from Thursday's deadly passenger plane crash may take four days as investigators work through freezing temperatures and piles of wreckage, a federal transportation official said Saturday.
Only a few pieces of the Continental Connection Dash 8 turboprop were recognizable after the crash.
"The medical examiner believes that three to four days are going to be required to recover the victims of this crash, and they're in the process of doing that," Steve Chealander of the National Transportation Safety Board said. "They've already pulled some of the folks out of there, but they've got a long way to go."
All 49 passengers aboard Continental Connection Flight 3407 died when the 74-seat Bombardier Dash 8 Q400 turboprop crashed into a home in Clarence Center, New York, on Thursday night. A 61-year-old man in the house died also, but his wife and daughter survived.
Fifteen bodies have been recovered, and efforts to identify the victims and conduct autopsies are under way, Erie County Health Commission Anthony Billittier said Saturday evening. A federal disaster mortuary team was called to assist local forensic officials.
Despite reports from local authorities who said the plane hurtled toward the house from a sharp nosedive, Chealander said the current orientation of the plane indicates that it fell flat on its belly.
Chealander said the recovery effort and the investigation have been hampered by freezing temperatures as authorities try to sift through the wreckage of the flight and the home it struck. Some parts of the plane have fallen as deep as the basement, he said.
"Keep in mind, there's an airplane that fell on top of a house," he told reporters. "The house and the airplane are together."
Authorities said it would probably take weeks to identify remains of the victims, with DNA testing required in many cases because of the intensity of the crash and subsequent fire.
A 2-square-mile area around the crash site, about 6 miles from the Buffalo airport where the plane was headed, remained sealed off Saturday as investigators sought to determine the cause of the crash. But the extent of the restricted area belied the concentrated force of the impact into the one house. Watch what investigators are saying »
Karen Wielinski was watching television inside the house when she heard a plane making an unusually loud noise.
"I thought to myself, 'If that's a plane, it's going to hit something,' " she told Buffalo radio station WBEN.
"And next thing I knew, the ceiling was on me," she said.
Wielinski and her daughter Jill, 22, were in the front of the home, and they escaped the house with minor injuries. Wielinski's husband, Doug, who was in the dining room, was killed.
On Friday, federal investigators released information from the plane's cockpit voice and flight data recorders, indicating that icing may have been a major factor in the crash.
The plane's pilot and co-pilot discussed "significant ice buildup" on the plane's windshield and wings as it descended toward the Buffalo airport. The plane underwent "severe" pitching and rolling motions after the landing gear was lowered and wing flaps were set for the approach, Chealander said.
There was a mix of sleet and snow in the area, but other planes landed safely at the airport about the time the flight went down.
Chealander said the flight crew reported that visibility was about 3 miles and there was snow and mist as they descended.
The voice and data recorders indicated that the plane's internal de-icing was on during the landing approach, he said.
"A significant ice buildup is an aerodynamic impediment," he added. Find out why »
Keith Burtis was driving about a mile from the crash site when he heard the impact.
"It was a high-pitched sound," Burtis said. "It felt like a mini-earthquake."
A ball of fire filled the night sky as the jet fuel erupted, Burtis said, and he saw a steady stream of fire trucks rush past as smoke billowed. At least nine volunteer fire departments responded. Watch iReporters' close-up accounts »
Among the passengers killed was Beverly Eckert, widow of a September 11 attack victim.
Also aboard was Alison Des Forges, senior Africa adviser for Human Rights Watch, one of her colleagues said. Des Forges spent four years in Rwanda documenting the 1994 genocide and had testified about the atrocity and the situation in central Africa to Congress and the United Nations, according to the organization. Read more about the victims
Also on the flight was Susan Wehle, a cantor at Temple Beth Am in Williamsville, outside Buffalo, a synagogue official said.
Colgan Air identified the crew as Capt. Marvin Renslow, the pilot; First Officer Rebecca Shaw, who was co-pilot; and flight attendants Matilda Quintero and Donna Prisco. In addition, an off-duty crew member, Capt. Joseph Zuffoletto, was onboard.
"This is easily the saddest day in the history of our airline," said Philip Trenary, the company's CEO.