A source said that according to flight data, there were smoke alerts near the airliner cockpit early Thursday in the minutes before it fell down.
The source added that data came through the Aircraft Communications Addressing and Reporting System (ACARS), a data link for sending messages between planes and ground facilities. A screen grab of data has time stamps matching the approximate time the aircraft went missing.
Aviation experts said that the alerts don't necessarily mean a fire occurred on the plane or that the crew even knew about the alerts.
"(The data) doesn't tell us anything, whether it's an explosion because of a bomb or because of a mechanical fault, but immediately it narrows down the area that we're looking at," CNN aviation analyst Richard Quest said. "We're now no longer worried about wings or what else might have happened, or other flight control surfaces."
The plane carrying 66 people crashed after disappearing from the radar while flying from Paris to Cairo. Egyptian officials say they suspect terrorism, but no group has claimed responsibility for it so far.
No survivors have been found, but some debris was found by searchers in the Mediterranean Sea on Friday. The searchers also found suitcases and human remains.
There were indications of problems with a heated window in the cockpit, a sliding window in the cockpit, smoke in the lavatory, smoke in the avionics compartment below the cockpit, a fixed window, the auto pilot and the flight control system.