Two small planes collided in flight Saturday and crashed in the Chino Hills area, killing at least two people, authorities said.
The dead were not identified and investigators suggested that there might be other casualties in the wreckage.
The Federal Aviation Administration said the accident occurred at 2:50 p.m. about two miles west of Euclid Avenue and California 71.
Collision, Then Fire
San Bernardino County Sheriff's deputies said a single-engine Cessna and a twin-engine Beechcraft collided, caught fire and then fell into an area of fields and steep hills. Upon impact, one plane slid into a ravine.
It was not known whether investigators had identified the planes' registration numbers.
The crash site is a remote area of steep hills and gulches accessible only by plane or four-wheel drive vehicles, police said. Those conditions were making it difficult for investigators to determine if there were any additional fatalities.
The two confirmed deaths were believed to be the pilots of the planes. It was unclear whether there were any passengers on board either plane.
Chino fire officials said the Beechcraft took off from Chino Airport, heading east, then circled to the west. The Beechcraft's pilot was last heard giving a routine report to the airport tower at 2:45 p.m.
The single-engine Cessna was believed to have departed from Corona Municipal Airport, about four miles from Chino Airport.
The FAA said both planes were flying in areas that are not monitored by air controllers.
Investigators from the National Transportation Safety Board arrived at the site Saturday night, but darkness hampered the inquiry. A full-scale investigation was expected to begin this morning, authorities said.
There have been several air accidents in the last 18 months in the area where Saturday's crash occurred. At least seven people have died in air crashes in the Chino Hills area since May, 1986.
"We've had numerous plane crashes over the years in this area," said Chino Fire Department Battalion Cmdr. Bruce Clark.
He blamed the area's poor safety record on the proximity of several airports as well as the steep terrain.
"We average an air crash every six to nine months in this area," he said.
Contributing to this article was Times staff writer Louis Sahagun in Chino Hills.