(AP) - A newspaper is reporting that the voice recorder indicates that one of the pilots was locked out of the cockpit before a Germanwings jetliner plummeted into a remote Alpine mountainside.

The New York Times is citing an investigator it doesn't identify as saying that the audio shows that after an ordinary start to the flight, one of the pilots left the cockpit and could not get back in.

The investigator told the newspaper that the pilot began knocking quietly on the door, then became more insistent, saying that eventually: "You can hear he is trying to smash the door down."

The investigator does not speculate as to why the other pilot didn't open the door or make contact with ground control before the plane crashed Tuesday. All 150 people aboard were killed.