Egyptian President Abdel Fattah al-Sisi said on Sunday that an investigation into the cause of an EgyptAir plane crash could take a long time but the facts would be made public as soon as they were available.

In his first public remarks on Thursday's crash, which killed all 66 people on board, Sisi said all possible scenarios were still being considered.

"This could take a long time but no one can hide these things. As soon as the results are out people will be informed," Sisi told assembled ministers and members of parliament at the opening of a fertiliser plant in the port city of Damietta.

EgyptAir flight MS804 crashed in the Mediterranean on its way to Cairo from Paris, killing all on board including 30 Egyptians and 15 French people.

Shortly before it disappeared off radar screens the plane sent a series of warnings indicating that smoke had been detected on board, French investigators said on Saturday.

The signals did not indicate what caused the smoke or fire but they offered the first clues as to what unfolded in the moments before the crash.

"Until now all scenarios are possible. So please, it is very important that we do not talk and say there is a specific scenario," he added.

Egypt said its navy had found human remains, wreckage and the personal belongings of passengers floating in the Mediterranean about 290 km (180 miles) north of Alexandria but the search for the black box recorders was continuing.