Air Algerie AH5017 black box tape 'unintelligible'
The cockpit voice recorder from the Air Algerie flight that crashed in Mali in July is damaged and unintelligible, French investigators say.
They said the team was unable to extract information from one of the two black boxes found in the wreckage.
Flight AH5017 went down en route to Algeria near the Malian town of Gossi, killing all 118 people aboard.
France took a leading role in the investigation after 54 of its citizens were killed in the crash.
French officials have said they believe bad weather was the likely cause of the crash on 24 July but have not ruled out other possible explanations.
The voice recorder used magnetic audio tape - common to older aircraft - but this was found broken and had to be repaired, Remi Jouty, president of France's BEA air accident investigator, told reporters at a press conference on Thursday.
"There is sound on the tape but it is unintelligible," he said.
"The device seemed to be recording but we don't yet know why it did not work, except that this was not a result of the crash itself," Mr Jouty said, adding that it may have been caused by a "simple technical problem".
The system of using magnetic tape has since been replaced by digital technology in modern aircraft.
Mr Jouty also said it seemed likely that the plane had broken up on impact instead of in the air, based on the strong concentration of debris in one area on the ground.
"When we look at the trajectory, this leads us to believe that the plane did not break up into several pieces while in flight," he said. "This does not exclude that damage was caused during the flight."
Meanwhile, the French army says investigators have left the site after transporting all useable DNA material to French laboratories, according to the BBC's Alex Duval Smith in Mali.
The Malian army is guarding the site, which includes a container full of the passengers' personal effects, she says.
Shortly before losing contact, the pilots of flight AH5017 had asked permission to change route due to bad weather after taking off from Burkina Faso.
In addition to the French citizens, there were also 27 victims from Burkina Faso and further passengers from, among others, Lebanon, Algeria, Canada and Germany. One victim was British.
All six members of the crew, who were Spanish, died in the crash.