Investigators have been unable to download the black box information recovered from the debris of the EgyptAir passenger plane that crashed in the Mediterranean last month.

Flight MS804 was flying from Paris to Cairo when it crashed into the sea on 19 May killing all 66 people on board.

The voice and data recorders will now be flown to Paris to have salt removed as the French aviation accident investigation bureau attempts to repair the damage.

The recorders will then be returned to Cairo for data analysis, according to the Egyptian investigative committee.

French and US investigators have overseen attempts to extract information from the black boxes as the recorders were produced by US company Honeywell, while the plane, an Airbus A320, was manufactured in France.

The pilots did not report distress before the crash and no-one has claimed responsibility bringing down the aircraft.

Black box memory units normally provide investigators with pilot conversations, engine data and information about the autopilot and navigation systems.

According to radar readings, the aircraft made violent movements after cruising in clear skies.

The Airbus A320 descended rapidly from 38,000ft to 15,000 before disappearing at 10,000ft.