(VOVworld) - One of the two pilots of the Germanwings plane that crashed in the French Alps was locked out of the cockpit, according to sources close to the investigation. German television channel BFM reported on Thursday that early findings from the cockpit voice recorder suggest the pilot made desperate efforts to get back in. A senior military official involved in the investigation was quoted as saying the black box data indicated one pilot was locked out of the cockpit and tried unsuccessfully to break his way back in. "The guy outside is knocking lightly on the door, and there is no answer," the investigator said. "And then he hits the door stronger, and no answer. There is never an answer." Experts told BFM TV that there may be two possibilities: one is that a pilot fainted due to decreasing pressure in the cockpit and could not open the door; the other is possibly a suicide. Investigations will now turn to the two pilots’ personal records. All 150 passengers on board were killed when the Germanwings flight 4U 9525 from Barcelona to Duesseldorf crashed in remote terrain, after an unexplained eight-minute descent in mid-flight.