YORBA LINDA, Calif. -- A former crash investigator said he's confident officials will figure out why a small plane broke apart in the air over a Southern California neighbourhood, raining down chunks of metal and igniting a house fire that killed four people.

The pilot, a retired Chicago police officer living in Nevada, also died. Investigators on Tuesday planned to continue collecting pieces of the plane that fell into homes across about four blocks in Yorba Linda, a community southeast of Los Angeles.

Aircraft that break apart while flying leave "fingerprints" -- tell-tale signs -- in the metal that will allow investigators to "build a sequence of the breakup that will lead them back to where it originated," said John Cox, a former commercial pilot who's head of the consulting firm Safety Operating Systems.

Witnesses described the plane coming out of the clouds in one piece and "then they saw the tail breaking off and then the wing breaking off and then something like smoke before the airplane impacted the ground," said Maja Smith, an investigator with the National Transportation Safety Board.

Those witnesses did not report an explosion while the twin-engine propeller-driven Cessna 414A was in the air, she said.

Pilot Antonio Pastini, 75, of Gardnerville, Nevada, was the only person aboard, Orange County Sheriff's Lt. Cory Martino said.

Authorities were trying to identify the people who died in the house, describing them only as two males and two females. Martino said DNA may be required because of the condition of the bodies.

The plane came down "in multiple pieces, about 4 or 5 pieces, with a long trail of smoke," said Kyle Vanderheide, 25, who was driving when he spotted it overhead.

Shawn Winch, 49, said he was in his backyard when he heard what "sounded like a missile coming at my house." He said he saw the plane veer off and debris falling.

"It wasn't intact," he said as the plane came toward the neighbourhood. "It was already breaking up."

One of the columns of a neighbour's home was collapsed and debris from the plane was strewn throughout the street. Another home had broken windows.

The aircraft, which can carry up to eight people, took off from the Fullerton Municipal Airport about 12 miles (19 kilometres) away, Federal Aviation Administration spokesman Allen Kenitzer said.

Preliminary radar data shows the plane reached about 7,800 feet (2,377 metres) and then rapidly fell, said Eliott Simpson, a NTSB investigator.

The main cabin of the airplane and one engine were found at the bottom of a ravine in the backyard of a house, and the other engine made a hole in the street, Simpson said.

A portion of the plane's right wing had not been found, and investigators would search the burned house, Smith said. The Cessna 414A carries fuel in its wings.

Video showed panicked residents running to the house as flames and dark smoke engulfed it. One man used a garden house to douse a burning wing that landed on the street.

Investigators will look into the maintenance record structural integrity of the aircraft, as well as the pilot's record, Smith said. The wreckage will be transported to Phoenix, Arizona, for a forensic examination.

------

Associated Press journalists John Antczak, Amanda Lee Myers and Christopher Weber in Los Angeles contributed to this report.