Egyptian President Abdel Fatah al-Sissi said “all scenarios” are being considered in the investigation of the crash of Egyptian airliner into the Mediterranean Sea last week but warned the media against speculation it was brought down by a terrorist attack.

“All scenarios are now being considered,” Sissi said in his first comments since the commercial jet disappeared Thursday from radar screens. He spoke Sunday at the opening of a fertilizer plant in northern Egypt, according to aired footage of the event.

“We should not say that one scenario is more likely,” he said. “The investigation will take time.”

EgyptAir Flight 804 from Paris to Cairo plummeted into the sea just after leaving Greek airspace about 2:30 a.m. Thursday, but the pilots sent no distress calls. The Airbus A320 had 66 people on board, including citizens from a dozen nations.

Investigators have found only small bits of wreckage that have provided few clues. Sissi also said Sunday that an Egyptian submarine capable of operating at roughly 10,000 feet below the surface had been dispatched to assist in recovery efforts.

On Saturday, French investigators said the plane sent multiple automated messages indicating smoke had been detected on board in the minutes before the crash.

Sebastien Barthe, a spokesman for the French civil aviation investigation agency, told the Associated Press that the messages “generally mean the start of a fire.” Authorities still cautioned that the cause of the crash was unclear.

Also Saturday, EgyptAir said that it had hired a foreign consultant to brief families on efforts to recover the victims, including DNA analysis. The government has housed families in hotels near the Cairo International Airport.

“The process of recovering the bodies of the victims [will] take a long time,” EgyptAir said in a statement. The airline urged the families to provide as much information as possible to speed the identification process.

Egypt’s military spokesman posted Saturday on Facebook what he said were the first images of debris recovered by naval ships in the Mediterranean, including a life vest, fabric from seat cushions and parts of the aircraft exterior.

Flight 804 departed Paris’s Charles de Gaulle airport at 11:09 p.m. Wednesday and was bound for Cairo when it crashed into the sea. The messages signaling that the aircraft detected smoke aboard the flight were first reported Friday by the industry publication Aviation Herald.

The website said smoke appeared in a lavatory near the cockpit, and that the information was transmitted through the plane’s Aircraft Communications Addressing and Reporting System.

The plane’s abrupt turns and ultimate descent into the Mediterranean have raised fears the flight was targeted by terrorists, but no group has so far claimed responsibility.

But with the bulk of the fuselage and flight recorders still missing, the tragedy has offered few tangible clues.

Cunningham reported from Istanbul.