France’s BEA (Bureau of Investigations and Analyses) said it has successfully extracted recordings from the cockpit voice recorder of the Germanwings plane that crashed in the French Alps on Tuesday.

BEA Director Remi Jouty said at a news conference at its headquarters outside Paris on Wednesday it could take days to get "usable" information from the voice recordings.

“Detailed work will be carried on the file to understand and interpret the voices and sounds that can be heard on the file,” Jouty said.

He also said he expected to have a more detailed analysis of the voices in “a matter of days.”

The flight data recorder, which according to experts is likely to provide more clues to the reason for the crash of the Airbus A320, hasn’t been found yet, Jouty said.

He added the crash scenario didn’t appear to be linked to depressurisation and he ruled out a mid-air explosion having taken place.

Earlier on Wednesday, German Chancellor Angela Merkel, French President Francois Hollande and Spanish Prime Minister Mariano Rajoy flew over the crash site to see the devastation for themselves. They also met residents of the village of Seyne-les-Alpes, where the salvaging operation has been set up.

The crash, which claimed the lives of all 150 people on board Flight 4U 9525, is the worst aviation disaster in France in 15 years. Most of the victims are German or Spanish.

Lufthansa said it still could offer no explanation why the aircraft run by its low-cost unit Germanwings crashed about 100 kilometres north of Nice en route to Duesseldorf in Germany from Barcelona in Spain.

"It is inexplicable this could happen to a plane free of technical problems and with an experienced, Lufthansa-trained pilot," Reuters quoted Lufthansa chief executive Carsten Spohr as telling reporters in Frankfurt.