Updated at 10 p.m.
Tim and Rhonda Willms witnessed the mid-air collision while hiking in Calabasas Monday afternoon.
"My wife and I ... were hiking along Craig Road in the Malibu Creek State Park. "It happened almost overhead of us," Tim wrote in an email to Patch.
The couple, who are visiting from out of town, said they became instantly aware that something catastrophic had happened.
"We already knew it was a plane crash as we saw a plane go down after hearing a very loud 'explosion' type sound," Time wrote. "Then we saw the smoke go up, very black."
Updated at 7:00 p.m.
Federal Aviation Administration spokesman Allen Kenitzer released the following preliminary information:
There was an mid-air airplane accident Monday northwest of Santa Monica, CA. The first airplane, a Cessna 172, with tail number N4677V, was westbound at 3,500 feet. The second airplane, also a Cessna 172 that had just departed Santa Monica for an engine test flight, was eastbound at 3,100 feet.
According to FAA radar data, the flights merged approximately 8 miles east-northeast of Ventura at 2:01 p.m.
The first airplane landed on the Westlake Village Golf Course. The second airplane crashed into mountainous terrain. The crash started a one-acre fire.
Updated at 6:45 p.m.
Human remains have been found near the crash site of the single-occupancy aircraft that went down in the hills between Malibu and Calabasas, and an official with the Los Angeles County Coroner was on his way to the scene, said L.A. County Fire Inspector Tony Imbrenda.
Updated at 6:35 p.m.
Los Angeles County Sheriff's Department spokesman Steve Whitmore
told Patch that the crashes of the two planes above Malibu and in Westlake Village are connected, but he declined to provide more details. He said the final determination will be made by federal investigators.
National Transportation Safety Board investigators are scheduled to arrive on scene at 6 a.m. Tuesday, Whitmore said.
Lt. Jim Royal of the sheriff's Malibu-Lost Hills station said a Los Angeles County Fire Department helicopter was flying a member of Malibu Search and Rescue, a county fire department official and a Federal Aviation Adminstration investigator to the crash site.
"We're trying to determine if we have a recovery or rescue effort," Royal said.
Helicopters were flying from the command post up into the crash site in the hills, while Search and Rescue crews were hiking up to the site, where 31 county firefighters were already on the scene.
Updated at 5:15 p.m.
About the same time that the plane-related fire broke out in Calabasas, a single-engine, fixed-wing aircraft made a hard landing at the Westlake Village Golf Course at 4800 Lakeview Canyon Road, according to county fire Inspector Tony Imbrenda. Three people were treated for minor injuries.
According to the FAA website, the fixed-wing, single-engine Cessna was manufactured in 1980. The owner was listed as AmeriFlyers of Florida LLC, with a Addison, TX, address.
There was no word from authorities if there was any relation between the
At 4:40 p.m., the area affected by Monday's brush fire in Calabasas has been revised to one-half an acre.
Possible plane wreckage was spotted in the middle of the brush fire.
The fire was reported at 2:04 p.m. near Mulholland Highway at Las Virgenes Road in Calabasas, according to the L.A. County Fire Department. The fire was fully contained as of 4:30 p.m.
Several helicopters were working to control the flames.
Investigators are trying to determine if the brush fire is related to the hard landing of a Cessna plane at a Westlake Village golf course. The plane, which is marked with an American Flyers decal, landed just after 2:15 p.m. American Flyers is a flight training operation out of Santa Monica, according to KABC.
A helicopter crew spotted possible plane wreckage in the area of the brush fire, according to L.A. County Fire Inspector Quvondo Johnson.
Crews were hiking up to the wreckage to investigate, Johnson said.
"It could be some debris that was already up there," Johnson said. "It could be something off the plane that went down off the golf course."
He added that it could also be from another plane, but that there was no official word yet.
Allen Kenitzer of the Federal Aviation Administration told Patch that the FAA is investigating.
"All I can confirm at this time is that we are working two possible airplane accidents, one is the Westlake area and another in the [Mulholland] Area," Kenitzer said.
Fire crews were searching the area for potential victims, City News Service reported.
Mulholland Highway was closed to eastbound traffic at Cornell Road, according to the Lost Hills/Malibu Sheriff's Station. Malibu Canyon Road was open.
Check back for more on this story.