LOS ANGELES (AP) - Three people have been killed in a pre-dawn helicopter crash in a rural area of northern Los Angeles County while filming for a reality TV show. Los Angeles County Fire dispatcher Robert Diaz said the crash occurred about 3:40 a.m. Sunday at the Polsa Rosa Ranch in Action. The ranch has been used as a film location. Diaz said everyone on board died. The three people aboard the helicopter have not been identified. Philip Sokoloski, a spokesman for FilmL.A., which processes filming permits for location shootings in the Los Angeles region, said a production company had been approved to use a helicopter for a reality TV show. The shoot was scheduled to go from Saturday afternoon into Saturday night. The circumstances surrounding the crash are still unknown, Federal Aviation Administration spokesman Allen Kenitzer said. He said the Bell 206B Jet Ranger had substantial damage. Both the FAA and the National Transportation Safety Board are investigating. Permit paperwork shows Bongo, Inc. was working on an untitled military-theme TV program. Records also show Crossbow Helicopters received approval to participate in filming from the Federal Aviation Administration. "We wouldn't have referenced helicopter activity if we didn't already have pre-approval from the FAA," Sokoloski said. According to its website, Polsa Rosa is a "movie ranch" where film crews can utilize a variety of terrains as well as two airstrips. The ranch, according to the Internet Movie Database, was used in "Windtalkers" and last year's remake of "Red Dawn." Tang reported from Phoenix.