Audio from the flight deck voice recorder of EgyptAir MS804 indicates an attempt to put out a fire on board the jet before it crashed into the Mediterranean, sources on the investigation committee said on Tuesday.

The Airbus A320 plunged into the eastern Mediterranean en route from Paris to Cairo on May 19. All 66 people on board were killed. The cause of the crash remains unknown.

Earlier analysis of the plane's flight data recorder showed there had been smoke in the lavatory and avionics bay while recovered wreckage from the jet's front section showed signs of high temperature damage and soot.

The flight deck recorder, taken to Cairo this week after being repaired at laboratories belonging to France's BEA aircraft accident agency, further indicate that a fire took hold of the plane in its final moments, the sources said.

The recordings usually capture pilot conversations and any cockpit alarms, as well as clues such as engine noise.

Investigators are to conduct further analysis on the voices contained in the recordings and have not yet ruled out any possibilities as to what caused the crash, the sources said.