Marie Gemmell, 36, and her two sons, 3-year-old Cole and one-month-old Devon, were killed when an aircraft smashed into their home in Gaithersburg, a Washington suburb in the US state of Maryland.

Mrs Gemmell found found lying on top of her young sons in a second-floor bathroom in an apparent effort to shield them from the smoke and flames, according to police Captain Paul Starks.

Her husband and a school-age daughter were not home and survived the devastating crash, which also killed the three people on board the plane. 

Among those on the aircraft was Dr Michael Rosenberg, the founder and CEO of North Carolina clinical research organisation Health Decisions. 

Fred Pedreira, who lives near the crash site, saw the plane come down.

He said: "This guy, when I saw him, for a fast jet with the wheels down, I said, 'I think he's coming in too low.'

"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.

"I said, 'My God, those are people in that plane."'

County fire department spokesman Pete Piringer told a news conference that the Embraer SA twin-engine Phenom 100 crashed into the home about one mile from the Montgomery County Airpark.

The crash resulted in a fire, which destroyed two homes and damaged three others.

Mr Piringer added that the fires had been contained but that some jet fuel had leaked into a stream.

A Federal Aviation Administration spokeswoman said the plane went down on its way back to the airport.

Witnesses told local media that the plane was spotted circling the area with the wheels down.

They said that the aircraft appeared to be struggling for control.

Robert Sumwalt, a National Transportation Safety Board member, said that the plane's fuselage crashed into the front lawn of an adjacent home.

He added that investigators believe that one of its wings, which had fuel inside, was sheared off and tore through the front of the Gemmell home.

The National Transportation Safety Board has sent a team to investigate the crash.

Mr Sumwalt added that the board planned to look into a range of potential causes of the crash, including crew experience and proficiency, training and procedures, equipment performance, weather and other environmental factors such as birds.