An Osprey aircraft with five Marines on board crashed in the Southern California desert Wednesday afternoon, officials said.
The status of the Marines wasn't immediately available. The 3rd Marine Aircraft Wing, an aviation squadron based in San Diego, said in a statement that it was "asking for patience as we work diligently with first responders and the unit to identify what occurred this afternoon."
The aircraft, an MV-22B Osprey, was based at Camp Pendleton, also in San Diego, the statement said.
Military officials said early reports of nuclear material on board the aircraft were false.
The crash was reported at 12:25 p.m. near Glamis, an area about 150 miles east of San Diego known for its desert sand dunes and other off-road attractions, Naval Air Facility El Centro said.
Military firefighters and the Imperial County Fire Department were responding, it said.
The Osprey — which can take off and land like a helicopter, but fly like an airplane thanks to its "tiltrotor" engines — has had a troubled history over the two decades it has been flying in U.S. military training exercises and missions.
In March, an Osprey crashed during training exercises with NATO allies in Norway, killing four U.S. Marines. The accident took place during extreme winter conditions.
Even though the Osprey was involved in crashes that killed more than 30 people before it went into service in 2007, the Marine Corps has stood behind the vehicle as relatively safe and effective.
This is a developing story. Please check back for updates.