Five Mairines died when the military plane they were on board crashed in southern California, a spokesman for their squadron said Thursday.

The accident occurred the day before near Glamis, 35 km from the Mexican border, and involved an MV-22B Osprey type aircraft participating in a training mission, said in its press release the 3rd Marine Aircraft Wing, based in San Diego.

The squadron has formally denied "rumors" that radioactive substances were on board the plane.

The American army has already experienced several accidents involving this model of Osprey aircraft, with vertical take-off, including one that killed four people last March in Norway during a NATO exercise.