PARIS- The co-pilot of the Germanwings airliner that crashed in the French Alps killing all 150 people aboard appears to have brought the A320 Airbus down deliberately, the Marseille prosecutor said today.

German Andreas Lubitz, 28, left in sole control of the Airbus A320 after the captain left the cockpit, refused to re-open the door and operated a control that sent the plane into its final, fatal descent, the prosecutor told a news conference.

The French prosecutor said Lubitz was not known as a terrorist and there were no grounds to consider the crash as a terrorist incident. Recordings suggested passengers' screams began just before the final impact, he said.

Earlier, a German state prosecutor had said that just one of the two pilots of the Germanwings airliner was in the cockpit at the time it went down.

The statements came after the New York Times reported that "black box" recordings showed one of the pilots had left the cockpit and could not get back in before the plane crashed.

"One was in the cockpit and the other wasn't," Christoph Kumpa at the prosecutors' office in Duesseldorf told, adding that the information came from investigators in France.

Investigators were still studying voice recordings from one of the "black boxes" on Thursday while the search continued for a second in the ravine where the plane crashed, 100 km (65 miles) from Nice.

The recordings did not make clear why the pilot left the cockpit or why he could not regain entry as the plane steadily descended toward a mountain range in a remote area of the French Alps on Tuesday.

"The guy outside is knocking lightly on the door and there is no answer," an investigator described only as a senior French military official told the New York Times, citing the recordings. "And then he hits the door stronger and no answer. There is never an answer."

"You can hear he is trying to smash the door down," the investigator added.