(CNN) -- A Marine who fell from an aircraft during a training exercise was found dead late Tuesday afternoon, the Marines reported.
Nobody knows how the Marine happened to fall out of the MV-22B Osprey on Monday, 1st Lt. Hector Alejandro, media officer for the 2nd Marine Aircraft Wing at Cherry Point, North Carolina, told CNN on Tuesday.
The aircraft had taken part in a training exercise at the airport in Elizabethtown, Bradley Kinlaw, Bladen County emergency management director, told CNN affiliate WECT.
A crew member noticed the Marine missing about half a mile past White Lake, WECT reported.
Alejandro said Marines in Ospreys are always supposed to be secured, either by seat belts or tether cables. He didn't know how the missing Marine was secured.
Lt. Col. Christian Harshberger with Marine Aircraft Group 26 said the tiltrotor Osprey's cargo bay door remains open during training operations, according to WECT.
The Osprey has the speed and range of a turboprop airplane but the vertical maneuverability of a helicopter.
More than 100 Marines had been brought in to search on the ground and in the air, Alejandro said.
The Marine's name was not immediately released. He was believed to have died from the fall, officials said.