Allen Kenitzer, a spokesman for the Federal Aviation Administration, said the aircraft went down under unknown circumstances.
The Orange County Coroner is working to positively identify those who died and notify next of kin, the sheriff's office said. One structure was involved and two victims were rushed to the hospital from the Southern California neighborhood where the accident took place.
Debris was left strewn around the neighborhood and the fuselage reportedly ended up in a backyard. "And then all of a sudden boom".
"I come out... it's raining plane parts from the sky", Jared Bocachica told the affiliate station.
It was not immediately clear what set the two-story house ablaze.
Video posted on social media sites showed panicked residents running to a suburban home that was engulfed in flames.
Witnesses said they felt shaking and heard loud noises when the plane hurtled to the ground, according to affiliate reports. One man used a garden house to douse a burning wing that landed on the street. Other photos show a nearby home damaged from debris with a propeller in its front yard.
"It's just devastating", she said.
The wreckage will be transported to Phoenix, Arizona, for a forensic examination, Simpson said.