No additional details were provided in the Marine Corps statement.
The MV-22B Osprey went down at 12:25 p.m. Wednesday during training in a remote area in Imperial County near the community of Glamis, about 115 miles (185 kilometers) east of San Diego.
The aircraft was based at Camp Pendleton with Marine Aircraft Group 39 and was part of the 3rd Marine Aircraft Wing headquartered at Marine Corps Air Station Miramar in San Diego, said Maj. Mason Englehart, a spokesperson for the wing.
The Osprey is a hybrid airplane and helicopter that has been criticized for its safety record. It can take off and land like a helicopter but transit as a turboprop aircraft.
Versions of the aircraft are flown by the Marine Corps, Navy and Air Force.
Prior to Wednesday’s crash, Osprey crashes had caused 46 deaths, the Los Angeles Times reported.
Most recently, four Marines were killed when a Marine Corps Osprey crashed on March 18 near a Norwegian town in the Arctic Circle while participating in a NATO exercise. In 2017, three Marines were killed when their MV-22B Osprey crashed off Queensland, Australia. In 2015, one Marine was killed and 21 were injured when their MV-22 Osprey caught fire during a “hard landing” in Hawaii.
The Osprey is a joint project of Bell Helicopter Textron and Boeing.
Its development was marked by deadly crashes, including an April 2000 accident in Arizona that killed 19 Marines.