Investigators were trying to determine Friday what caused a jet to smash into a hangar at Chino Airport while mechanics were conducting a test on the engine.
There were no immediate reports of injuries in the Thursday accident, officials said.
The Challenger aircraft was positioned on a ramp while the mechanics worked on it, and it jumped the rubber stops, said Ian Gregor, a spokesman for the Federal Aviation Administration.
There were three mechanics on the plane, he said. The plane was not intended for flight, said Gregor, citing preliminary information gathered by the agency.
The fixed-wing multi-engine aircraft is registered to Grady International in Irvine, according to online FAA records.