The man piloting a small plane that broke apart over a Southern California neighborhood had false credentials identifying him as a retired Chicago police officer, authorities said Tuesday, but they still had no immediate answers for the cause of the crash.

Antonio Pastini was killed when the twin-engine plane he was piloting broke up shortly after takeoff and fell in pieces in Yorba Linda, igniting a fire in a home where four people died on Sunday. Pastini, 75, was initially identified as a retired officer but Chicago police spokesman Anthony Guglielmi said there were no records of him working for the department.

Orange County sheriff's spokeswoman Carrie Braun said the credentials recovered from Pastini were not legitimate, but that the pilot was indeed Pastini.

Aviation safety experts cautioned against drawing early conclusions about the cause of the crash.

"At this stage you don't make assumptions. You let the evidence lead you where it leads you," said John Cox, a former commercial pilot and a veteran crash investigator who is head of the consulting firm Safety Operating Systems.

National Transportation Safety Board investigators have been collecting parts of the aircraft, the plane's records and information about Pastini, who was described as a commercial pilot with an instrument flight rating.

Preliminary information showed the plane took off around 1:35 p.m. Sunday from Fullerton Municipal Airport, made a left turn and climbed to an altitude of 7,800 feet (2,377 meters) before starting to descend over Yorba Linda.

Weather was intermittently rainy across Southern California during the weekend, but specific conditions the flight encountered were not immediately known.

Observers said the plane initially appeared intact when it fell through a cloud ceiling at an altitude of about 2,000 to 3,000 feet (600 to 900 meters), investigator Maja Smith said.

"Witnesses say that they saw the airplane coming out of a cloud at a very high speed before parts of the airplane such as tail and subsequently wings starting to break off," she said.

The Cessna 414A has good reputation, said Cox, who said he has flown similar Cessnas since the 1970s. In-flight break ups are uncommon, and causes can range from metal fatigue to instrument failure and forces induced by the pilot, he said.

He said the break up may have begun earlier than was apparent to the witnesses.

"Small pieces may have come off that are leading up to the cataclysmic break up that people see. You need to make sure that the airplane was fully intact when they first see it," he said. "As an investigator you have to be careful about that."

Losing control of an airplane can also lead to a break up.

"If you lose control of an airplane you can put enough load on it that it will actually fail, something will break," Cox said.

One of the first things that might fail in that situation, he said, is a horizontal stabilizer — the structures that look like small wings on the tail.

"Once one of them comes off the loads then on the airplane will exceed what it can then withstand and other pieces will fail due to structural overload," Cox said.

Photos of the wreck showing the outer portions of the wings apparently snapped off are consistent with the type of forces wings are subjected to with the loss of one or more horizontal stabilizers and the airplane loses aerodynamic balance, he said.

Video showing puffs of smoke erupting in the sky as the plane fell were consistent with an in-flight break-up rather than an in-flight fire aboard the plane, Cox said

Witnesses described the plane as sounding like a missile or a racing motorcycle. Cox said that could be the result of the engines no longer being under control.

The victims inside the home have yet to be publicly identified.

Associated Press journalists Amanda Lee Myers and Michael Balsamo contributed to this report.