A small, private jet has slammed into a house in the US state of Maryland, killing a woman and her two young sons inside the home and three people on the aircraft, authorities said.
The jet crashed around 10.45am local time in Gaithersburg, a surburb of Washington, DC, an official said.
Authorities quickly said all three people in the plane had been killed, but it took hours for fire crews to sweep the home and confirm that three people were inside.
They were identified as 36-year-old Marie Gemmell and her two sons, three-year-old Cole and one-month-old Devon, police said.
They were found in a second-floor bathroom. Ms Gemmell was lying on top of her young sons in an apparent effort to shield them from the smoke and fire, said police Captain Paul Starks.
Her husband and a school-age daughter were not home and were accounted for, police said.
The fuselage of the jet crashed into the front lawn of an adjacent home, which was heavily damaged by fire, and investigators believe one of its wings, which had fuel inside, was sheared off and tore through the front of the Gemmell home, said Robert Sumwalt, a National Transportation Safety Board (NTSB) member.
Witnesses reported seeing and hearing a secondary explosion after the plane hit the ground.
The two-storey, wood-frame home was gutted. The first floor was nearly completely blown out and smoke drifted from a gaping hole in what was left of the collapsing roof. No-one was injured in the adjacent homes that also had major damage.
The founder and CEO of a North Carolina clinical research organisation was among those on the plane. Health Decisions of Durham, North Carolina, said that Dr Michael Rosenberg was among those killed.
Dr Rosenberg was a pilot who crashed a different plane in Gaithersburg on March 1, 2010, according to a government official. Investigators are still trying to determine if Dr Rosenberg was at the controls at the time of yesterday's crash.
Fred Pedreira, 67, who lives near the crash site, said he had just returned home and was parking his car when he saw the jet and immediately knew something was wrong.
"This guy, when I saw him, for a fast jet with the wheels down, I said, 'I think he's coming in too low,'" Mr Pedreira told The Associated Press. "Then he was 90 degrees - sideways - and then he went belly-up into the house and it was a ball of fire. It was terrible.
"I tell you, I got goosebumps when I saw it," Mr Pedreira said. "I said, 'My God, those are people in that plane.'"
The Embrarer EMB-500/Phenom 100 twin-engine jet, which seats six people, was on approach to Montgomery County Airpark, which is about a mile from the crash site, officials said.
A team of NTSB investigators recovered the cockpit voice and flight data recorders from the downed plane.
The agency planned to look into everything that could have led to the crash, including crew experience and proficiency, training and procedures, equipment performance, weather and other environmental factors such as birds.