All five Marines on board a US military aircraft that crashed in southern California were confirmed dead on Thursday.

The MV-22B Osprey came down in Imperial County near Highway 78 and the town of Glamis, around 30 miles north of the Mexican border, and more than 150 miles east of San Diego, says The San Diego Union-Tribune.

Rescuers were searching for a fifth person who was onboard the aircraft, according to dispatchers.

The crash was confirmed by Naval Air Facility El Centro, which is around 30 miles from the crash site, the US media reported.

“NAFEC has just received reports of a downed aircraft in the vicinity of Coachella Canal Road and Highway 78. Installation, federal fire and Imperial County Fire Department are responding,” stated Naval Air Facility El Centro’s Facebook page.

The crash involved an MV-22B Osprey aircraft, which is a tiltrotor aircraft that can take off and land like a helicopter and fly like an airplane by pivoting its rotors.

The aircraft was from the 3rd Marine Aircraft Wing, an aviation unit headquartered at marine corps air station Miramar, in San Diego.

The plane had gone down in Imperial County near the Glamis Dunes, Naval Air Facility El Centro said in a Facebook post.

The facility, which is 15 miles north of the Mexican border in the Imperial Valley, trains Navy pilots, as well as aviators from other branches of the military.

The Pentagon confirmed the crash but denied reports that there were nuclear materials onboard.

The incident was the second military aircraft crash in Southern California in a week. An American Navy fighter jet crashed in the Mojave Desert last week, killing the pilot.

The military denied reports the aircraft was carrying radioactive material when it came down near Glamis, just 35 kilometres from the Mexican border. "We can confirm that an aircraft belonging to 3d Marine Aircraft Wing crashed near Glamis," a spokesman told AFP. "Five marines were on board the aircraft, and we are awaiting confirmation on the status of all members of the crew.

"Military and civilian first responders are on site. Contrary to social media rumours, there was no nuclear material on board the aircraft."

The aircraft was identified as an MV-22B Osprey, based at Marine Corps Air Station Camp Pendleton.

The US military has suffered a number of crashes with the aircraft, including an accident in Norway in March that left four marines dead.