Egypt's president says a submarine belonging to his country's Oil Ministry has left for the site of the crash of EgyptAir Flight-804 in the eastern Mediterranean.

President Abdel-Fattah el-Sissi says the submarine has the capacity to operate at a depth of 3,000 meters (9842 feet) below the surface. He says the submarine left Sunday to join the search for the cockpit voice and flight data recorders, commonly known as black boxes.

Making his first public comments since the Thursday crash of the Airbus A320 while en route from Paris to Cairo, el-Sissi says 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.