The cockpit voice recorder of the crashed EgyptAir flight MS804 indicates an attempt to put out a fire on board the jet before it plunged into the Mediterranean, sources on the investigation committee have said.

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

One of the black boxes was recovered from the bottom of the sea. The box recorded the data of flight MS804 until it stopped at an altitude of 37,000ft (11,250 metres), Egypt’s aircraft accident investigation committee said in a statement last Wednesday.

Analysis of the plane’s flight data recorder showed that there had been smoke in the toilets and avionics bay. 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 aircraft accident agency, further indicates 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.

The plane was carrying 56 passengers and 10 crew when it crashed, including 40 Egyptians, 15 French citizens, two Iraqis, two Canadians and one passenger each from Algeria, Belgium, Britain, Chad, Portugal, Saudi Arabia and Sudan.

Since the crash, small pieces of the wreckage and human remains have been recovered while the bulk of the plane and the bodies of victims are believed to be under the sea. A Cairo forensic team has received the human remains and is carrying out DNA tests to identify the victims.