Debris is seen at the crash site of Air Algerie flight AH5017 near the northern Mali town of Goss. Picture: Stringer

Le Bourget -

French investigators trying to pinpoint the cause of the Air Algerie crash in northern Mali say the black box that recorded conversations between the pilots is unreadable.

Remi Jouty, president of France's national aviation safety agency, says some of the plane's recording devices allowed investigators to trace its fast descent through stormy weather on July 24, but the probe had not yet excluded other possible causes, including error or deliberate actions in the crash.

All 116 people on board were killed, nearly half of them French.

Jouty said on Thursday it wasn't clear why - or when during the flight - the recorder malfunctioned on the MD-83. - Sapa-AP