Voice recordings show one pilot locked out cockpit

A black box voice recorder from the German Airbus operated by Lufthansa's Germanwings budget Airbus A320 crash is seen in this photo released March 25, 2015 by the BEA, France's Bureau d'Enquetes et d'Analyses (Air Accident Investigator).  [Photo/Agencies]

However, while Hollande promised that authorities would not rest until the causes of the crash were known, France's BEA air incident investigation bureau said it was still far too early to draw meaningful conclusions on why the plane, operated by the Germanwings budget arm of Lufthansa, went down.

"We have not yet been able to study and to establish an exact timing for all the sounds and words heard on this file," he said.

He expected initial analysis in "a matter of days" but that rough read-out could be subject to errors and that more work would be needed for a full interpretation.

Although he said "words" had been heard on the tape, Jouty would not confirm whether that meant the Airbus A320's pilots were conscious and he gave no details of the recordings.

Interior Minister Bernard Cazeneuve earlier said a terror attack was not the main hypothesis being worked on. Jouty said, however, that no theory could be excluded at this point.

While stressing it was too early to form a clear picture, he ruled out a mid-air explosion having taken place and said the crash scenario did not appear to be linked to depressurisation.

Jouty said the second black box had not yet been found but could not confirm Hollande's remark that its casing had. Among the new details, he said the airliner had flown in a straight line directly into the mountain - but would not say whether that suggested at the hand of a pilot or auto-pilot.

Germanwings said 72 Germans were killed in Tuesday's crash, the first major air passenger disaster on French soil since the 2000 Concorde accident just outside Paris. Spanish officials said 51 Spaniards were among the victims.