Egypt said on Friday its navy had found human remains, wreckage and the personal belongings of passengers floating in the Mediterranean, the first confirmation that an EgyptAir jet with 66 people on board had plunged into the sea.
Unconfirmed reports about flight data from the Airbus plane that disappeared while flying from Paris to Cairo in the early hours of Thursday local time pointed to several problems that its veteran pilot may have struggled with minutes before the crash.
"The Egyptian navy was able to retrieve more debris from the plane, some of the passengers' belongings, human remains, and plane seats," the Civil Aviation Ministry said in a statement.
President Abdel Fattah al-Sisi offered condolences for those on board.
The navy was searching an area about 290 km (180 miles) north of Alexandria, just south of where the signal from the plane was lost early on Thursday.
There was no sign of the bulk of the wreckage, or of a location signal from the "black box" flight recorders that are likely to provide the best clues to the cause of the crash.
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.
Egyptian Prime Minister Sherif Ismail said it was too early to rule out any cause for the crash. The aviation minister said a terrorist attack was more likely than a technical failure, but offered no evidence.
Although early suspicion centered on Islamist militants who blew up another airliner over Egypt seven months ago, no group had claimed responsibility more than 36 hours after the disappearance of flight MS804, an Airbus A320.
CNN reported on Friday that flight data, from an automatic system called the Aircraft Communications Addressing and Reporting System (ACARS), said smoke alerts were triggered aboard the EgyptAir jet shortly before it crashed.
ACARS routinely downloads flight data to the airline operating the aircraft.
Two U.S. officials told Reuters they could not confirm CNN's report. But they said an electronic sensor system had detected some kind of disturbance outside the jet around the time investigators believe it began falling from cruising altitude.
One of the officials said the disturbance outside the aircraft may have been caused by its sudden and rapid breakup, but it also could have been generated by some kind of mechanical fault or accident or a possible explosion or attack.
The officials asked for anonymity when speaking about the still-evolving investigation.
A screen grab of the flight data transmitted by ACARS to operators on the ground, published on the website of the aviation journal AVHerald.com, indicated failures in the jet's flight control system and alerts related to smoke in a lavatory and the avionics system, minutes before the crash.
The screen grab provided on the website showed only very terse messages sent from the aircraft, such as "SMOKE LAVATORY SMOKE," "AVIONICS SMOKE" and "F/CTRL SEC 3 FAULT."
The U.S. officials said they could not confirm the authenticity the data, however, and EgyptAir officials could not be reached for immediate comment.