French investigators on Wednesday searched for the reason why a German Airbus plowed into an Alpine mountainside, killing all 150 on board including 16 teenagers returning from a school trip to Spain, report Reuters.
Helicopters flew over the site where the A320 operated by Lufthansa's Germanwings budget airline disintegrated after it went down in a remote area of ravines en route to Duesseldorf from Barcelona. Police investigators made their way across the mountains on foot.
No distress call was received before the plane crashed on Tuesday, but French authorities said one of the two "black box" flight recorders, the cockpit voice recorder, has been recovered from the site 2,000 meters (6,000 feet) above sea level.
"The black box has been damaged. We will have to put it back together in the next few hours to be able to get to the bottom of this tragedy," French interior minister Bernard Cazeneuve told RTL radio, adding the box was still viable.
Cazeneuve said the fact debris was scattered over a small area of about one and a half hectares showed the plane likely did not explode in the air, meaning a terrorist attack was not the most likely scenario.
French Civil aviation investigators are expected to hold a news conference on Wednesday afternoon.
In Washington, the White House said the crash did not appear to have been caused by a terrorist attack. Lufthansa said it was working on the assumption that the tragedy had been an accident, and any other theory would be speculation.