An EgyptAir jet sent a series of signals indicating that smoke had been detected on board before it crashed into the Mediterranean on Thursday, France's air accident investigation agency said today.
A spokesman for the BEA agency said the signals did not indicate what caused the smoke or fire on board the plane, which plunged into the sea with 66 people on board as it was heading from Paris to Cairo.
But they offered the first clues as to what unfolded in the moments before the crash.
Egypt said its navy had found human remains, wreckage and the personal belongings of passengers floating in the Mediterranean about 290 km (180 miles) north of Alexandria.
Analysis of the debris and recovery of the black boxes are likely to be key to determining the cause of the crash - the third blow since October to Egypt's travel industry, still reeling from political unrest following the 2011 uprising that ousted Hosni Mubarak.
A suspected Islamic State bombing brought down a Russian airliner after it took off from Sharm el-Sheikh airport in late October, killing all 224 people on board, and an EgyptAir plane was hijacked in March by a man wearing a fake suicide belt.
Hunt For Black Boxes
He added that the priority now was to find the two flight recorders, known as black boxes, containing cockpit voice recordings and data readings, from the Airbus A320 which vanished from radar early on Thursday.
That would place the black box locator beacons, which last for 30 days, on the edge of their detectable range from the surface using acoustic equipment typically used during the first stages of a search, according to a report into the 2009 crash of an Air France jet in the Atlantic.
Aviation website Aviation Herald published a burst of seven messages broadcast over the space of three minutes. These included alarms about smoke in the lavatory as well as the aircraft's avionics area, which sits under the cockpit.
"The question now is whether the fire that caused the smoke was the result of an electrical fault - for example a short-circuit caused by damaged wiring - or whether some form of explosive or incendiary device was used - for example by a terrorist - to generate a fire or other damage," aviation safety expert David Learmont said.
The ACARS data suggested the fire had spread fast and "that might explain the fact that there was no distress call," Learmont wrote in a blog.
The aircraft was carrying 56 passengers, including a child and two infants, and 10 crew, EgyptAir said on Thursday. They included 30 Egyptian and 15 French nationals, along with citizens of 10 other countries.
"At this very moment all scenarios are being examined and none is being given greater emphasis," French Foreign Affairs Minister Jean-Marc Ayrault told reporters after meeting relatives of the victims of the EgyptAir crash.
"Searching for the aircraft is the priority, finding the 'black boxes' will help answer the legitimate questions raised (by the families)," Ayrault said.
France sent a plane and a navy ship to assist with the searches for the jet and three representatives of the BEA, together with an expert from Airbus, were in Cairo to help with the investigation.
The naval search is centred on an area north of Alexandria, just south of where the signal from the plane was lost early on Thursday.
EgyptAir Chairman Safwat Moslem told state television that the radius of the search zone was 40 miles, giving an area of 5,000 square miles, but said it may be expanded.
A European satellite spotted a 2 km-long oil slick in the Mediterranean, about 40 km southeast of the aircraft's last known position, the European Space Agency said.
Probe Reveals Brazil Plane Crashed One Minute After Pilots Sensed Trouble The Super Mario Bros. Movie Box Office Collections Hit $1 Billion, Joins the Club in Less Than a Month The Super Mario Bros. Movie Opens with $377 Million at the Worldwide Box Office Mamata Banerjee's Sunday Ultimatum To CBI For Death Penalty In Rape-Murder How Extreme Weather Is Leading To Rise In Child Marriages In Pakistan "Prove With Pics Crime Scene Intact": Court To Bengal Over Hospital Vandalism Egyptian Ship Arrested At Paradip Port In Odisha For Outstanding Debt Will Back Any Candidate Announced As Chief Minister Face: Uddhav Thackeray Trump, Musk, And The Importance Of 'Exaggeration' In Storytelling Track Latest News Live on NDTV.com and get news updates from India and around the world.