The U.S. Marine Corps shared Thursday that an Osprey aircraft crash in the California desert killed 5 Marines that were on board.

The MV-22B Osprey crashed at 12:25 p.m. Wednesday during a training mission near Glamis, California. The exact cause of the crash is under investigation, though it is currently being reported as the result of a “mishap.” The identities of the five Marines killed have not been released so the families can still be notified first, the U.S. Marine Corps said in a statement on Wednesday.

In a follow-up statement, the Marines shared their grief with the families of those who died in the crash.

“We mourn the loss of our Marines in this tragic mishap. Our hearts go out to their families and friends as they cope with this tragedy,” said Gen. Bradford J. Gering, commanding general of the 3rd Marine Aircraft Wing in a statement on Thursday.

Spokesperson Maj. Mason Englehart confirms that the aircraft was based at Camp Pendleton with Marine Aircraft Group 39 and was part of the 3rd Marine Aircraft Wing headquartered at the Marine Corps Air Station Miramar in San Diego.

The Osprey is known for its ability to safely take off and land like a helicopter but still have turbo aircraft speed, and different versions are used throughout different branches of the military.

The U.S. Marine Corps mainly uses it for the “Transportation of troops, equipment and supplies from ships and land bases for combat assault and assault support,” according to the Navy.