One person was killed in a mid-air collision of two small planes in California, the Los Angeles County Sheriff's Department confirmed to ABC News.

Investigators will be at both crash sites today, the National Transportation Safety Board told ABC News. The NTSB has taken over the investigation and will be looking at every detail of the crash, including inspecting engines and speaking with survivors and witnesses. A spokesperson for the NTSB said the investigation should take two to three days.

Both airplanes were a Cessna 172 and were northwest of Santa Monica. The first plane was west bound at 3500 feet. The second plane was east bound at 3100 feet and had just departed for an engine test flight, according to the Federal Aviation Administration. The flights merged approximately eight miles northeast of Ventura, Calif. at 2 p.m. yesterday.

The FAA said the first airplane landed on the West Lake Village Golf Course, all three passengers in the plane received non-life threatening injuries and were taken to a local hospital. West Lake Village Golf Course did not immediately return a request for comment. Witnesses told ABC News affiliate KABC Los Angeles that the plane made a hard landing on the golf course and spun around. The plane did not catch fire.

The second airplane crashed into mountainous terrain in Calabasas and started a one-acre fire. The deceased passenger was found with the second plane.

KABC reported the second plane was marked with an American Flyers decal, a flight training operation out of Santa Monica. American Flyers could not be reached for comment.

None of the departments involved in the investigation would release the names of the deceased victim or survivors.