Smoke was detected on the doomed Egyptair plane shortly before it crashed over the Mediterranean Sea, the French air accident investigation agency BEA said on Saturday.
But the agency cautioned that no conclusion could yet be drawn as to what caused Egyptair Flight MS804 to crash on Thursday with 66 people on board.
The BEA spokeswoman told dpa that smoke was detected in a forward lavatory, according to the information sent via ACARS, or Aircraft Communications Addressing and Reporting System, which transmits short condition updates to ground stations by radio or via satellite.
French Foreign Minister Jean-Marc Ayrault said reports of a smoke alarm onboard the Airbus A320 did not provide any concrete clues as to whether a technical error or terrorism brought down the plane.
The investigations would carry on in all possible directions, and no possibility would be ruled out, he added.
An official in the Egypt-led investigation commission denied the report of lavatory smoke to dpa.
"In his last contact with air controllers five minutes before the crash, the plane's pilot did not report anything unusual or a fire," the official said on condition of anonymity because he was not authorized to talk to media.
"It is too early to determine the cause of the crash," he said.
Three French aviation accident investigators and a technical expert from Toulouse-based manufacturer Airbus, the manufacturer of the plane, are currently in Cairo to help with the investigation.
The airliner vanished early Thursday shortly after leaving Greek airspace en route from Paris to Cairo.
On Saturday, the Egyptian military released the first photos of the wreckage retrieved from the crashed jet.
The still images and a video were posted on the army spokesman's Facebook page. They show what appear to be pieces of the fuselage as well as seats, a yellow life jacket and passengers’ personal belongings.
Body parts, luggage and airline debris were retrieved Friday from Mediterranean Sea around 290 kilometres north of the Egyptian coastal city of Alexandria.
Search teams were Saturday scouring the area for more debris from the jet and its two black boxes.
The airliner was flying at a height of 37,000 feet (11,300 metres) when it went missing about 45 minutes before its expected landing in Cairo.
Before disappearing from radar, data indicated that the plane swerved sharply and then began to make a steep descent, according to Greek data.
The likelihood that it was the victim of a terrorist attack was "far higher than the likelihood that the plane developed a technical failure," Egyptian Civil Aviation Minister Sherif Fathy said Thursday.