French investigators say usable data has been extracted from the cockpit voice recorder of Germanwings 4U 9525 but it has so faryielded no clues as to the cause of the plane's crash.
They said the plane hit the ground in the French Alps at great velocity, suggesting no explosion in flight.
Flight 4U 9525 from Barcelona to Duesseldorf crashed after an eight-minute rapid descent on Tuesday.
The French, German and Spanish leaders visited the crash site on Wednesday.
Remi Jouty, the director of the French aviation investigative agency, said there were sounds and voices on the cockpit voice recorder but that it was too early to draw any conclusions.
There had been earlier reports that the second black box - the flight data recorder - had been found. But Mr Jouty said this was not the case.
'Flying to the end'Mr Jouty said the plane's last communication was a routine one with air traffic control.
The plane confirmed instructions to continue on its planned flight path but then began its descent a minute later.
Mr Jouty said controllers observed the plane beginning to descend and tried to get back in contact with the pilots but without success.
He ruled out an explosion, saying: "The plane was flying right to the end."
He added: "The plane hit with great velocity, so parts are scattered over a great distance and have broken up into very small pieces."
Mr Jouty said: "At this stage, clearly, we are not in a position to have the slightest explanation or interpretation on the reasons that could have led this plane to descend... or the reasons why it did not respond to attempts to contact it by air traffic controllers."