Search teams have retrieved the cockpit voice and flight data recorders from the EgyptAir plane which crashed into the Mediterranean in May, killing all 66 on board.
It is hoped analysis of the black boxes will shed light on why the plane crashed en route from Paris to Alexandria.
At present no militant group has claimed responsibility for bringing down the aircraft.
Smoke was detected in multiple places on the EgyptAir plane before it crashed, French investigators said.
Spokesman Sebastien Barthe said the plane's automatic detection system sent messages indicating smoke a few minutes before it disappeared from radar on Thursday morning.
He said the messages "generally mean the start of a fire".
He added: "We are drawing no conclusions from this. Everything else is pure conjecture."
It follows reports on aviation industry website AVHerald.com on Friday that smoke was detected near the cockpit of the plane, which vanished over the Mediterranean.
Investigators also said the priority is to find the flight's data recorders of the missing jet.
Work has begun on analysing data from the two black boxes from the fated EgyptAir flight that crashed into the sea in May.
French air accident investigators confirm the signal detected earlier is from a flight recorder.
The head of Egypt's forensics authority said it is 'too early' to know what caused the EgyptAir plane to crash into the Mediterranean sea.