A submarine from the Egyptian oil ministry is heading to the site of the crash of EgyptAir Flight 804 to join the search for the cockpit voice and flight data recorders, or black boxes, the country's president said.
Abdel-Fattah el-Sisi also said Egypt was jointly investigating the crash with the French government.
"It is very, very important to us to establish the circumstances that led to the crash of that aircraft," he said, in comments broadcast live on Egyptian TV channels on Sunday.
He said the submarine, which has the capacity to operate at a depth of 3,000 metres (9,842 feet) below the surface, left for the site on Sunday.
Making his first public comments since the crash of the Airbus A320 in the eastern Mediterranean while en route from Paris to Cairo, el-Sisi said it "will take time" to determine the exact cause of the crash, which killed all 66 people on board.
He thanked the nations that have joined Egyptian navy ships and aircraft in the search for the wreckage and began with a minute's silence in remembrance of the victims.
El-Sisi also cautioned the media against premature speculation on the cause of the crash.
"There is not one scenario that we can exclusively subscribe to, all scenarios are possible," he said.
El-Sisi spoke a day after the leak of flight data showing trouble in the cockpit and smoke in a plane lavatory aboard the doomed aircraft, bringing into focus the chaotic final moments of the flight, including a three-minute period before contact was lost as alarms on the plane screeched one after another.
Officials have been cautioning that it was still too early to say what happened to the aircraft, but mounting evidence points to a sudden, dramatic catastrophe that led to the crash.