The people who died on Thursday were believed to have been on the plane, while those injured were inside the building.
The deceased victims will be identified after officials have contacted the next of kin, the Fullerton Police Department said in a statement.
Active Investigation Update:— Fullerton PD (@FPDPIO) There are two confirmed fatalities, ten individuals were transported to area hospitals for treatment and eight individuals were treated and released on scene. The investigation is on going. https://t.co/CiLra4HYFvJanuary 3, 2025
Eleven people were taken to hospitals, while eight were treated and released at the scene, police said.
The plane crashed less than two minutes after taking off from the Fullerton Municipal Airport in Orange County, 10km from Disneyland, according to the flight-tracking website FlightAware.
Security camera footage from Rucci Forged, a wheel manufacturer across the street, shows the plane was tilted on its side as it dove into the building, causing a fiery explosion and black plume of smoke.
Firefighters and police arrived on scene and battled the blaze and evacuated surrounding businesses, Fullerton police spokeswoman Kristy Wells said.
Chris Villalobos, an airport operations worker, went to the warehouse to see what had happened after receiving a phone call about a plane going down nearby.
He noted the airplane's owner was a regular at the airport and has frequently taken off from there.
"He has a hangar here and everything," Villalobos said.
After taking off, the pilot told air traffic control he was going to turn around to make an emergency landing, but it was unclear what the issue with the plane was, Villalobos said.
The building struck by the plane was occupied by Michael Nicholas Designs, a furniture upholstery manufacturer, according to a sign on a door.
The plane crash on the roof of a manufacturing building left a gaping hole. (AP PHOTO)
There appeared to be sewing machines and textile stock inside.
The Federal Aviation Administration is investigating the accident and identified the plane as a single-engine, four-seat Van's RV-10.
The National Transportation Safety Board said it also is investigating.
The airport in Fullerton has one runway and a heliport.
Metrolink, a regional train line, is nearby and flanks a residential neighbourhood and commercial warehouse buildings.
The Fullerton City Council posted a statement on social media calling the crash a "solemn tragedy".
Another four-seat plane crashed into a tree 600 metres from the airport in November while making an emergency landing shortly after take-off, The Orange County Register reported.
Both people on board suffered moderate injuries.
Fullerton is a city of about 140,000 people 40km southeast of Los Angeles.
