Flight MS804 had been en route from Paris to Cairo on May 19 when it plunged into the Mediterranean, killing all 66 people onboard.

Egyptian investigators said automated electronic messages sent by the plane show that smoke detectors went off in a toilet and in the avionics area, which lies below the cockpit, minutes before the plane disappeared, the BBC reported.

The investigators have now said that the recorded data from the black box are consistent with those messages.

Both voice and flight data recorders were recovered from a depth of around 3,000 metres in the Mediterranean. The second black box is still being repaired in Paris.

The front section of the aircraft’s wreckage also shows “signs of high temperature damage” and soot, the Egyptian investigation committee said.

The cause of the crash itself however, remains unknown. There was no distress call made from the plane before the crash.