Egypt says traces of explosives have been found on bodies from the EgyptAir crash in May, which killed all on board.
A ministry statement issued overnight says a criminal investigation will now begin into the crash of Flight 804.
The Airbus A320 plunged into the eastern Mediterranean en route from Paris to Cairo on May 19. All 66 people on board were killed.
The cause of the crash remains unknown.
No one has claimed to have attacked the plane.
The crash came seven months after a Russian airliner crashed in the Sinai Peninsula shortly after taking off from an Egyptian Red Sea resort, killing all 226 people on board.
The local affiliate of the extremist Islamic State group said it had downed the Russian plane with an explosive device planted on board.
Russia said the aircraft was likely downed by explosives.
France's accident investigation agency has said that smoke detectors went off during Flight 804's final moments. Spokesman Sebastien Barthe told the Associated Press this year that such messages "generally mean the start of a fire".
Industry publication Aviation Herald has reported that sensors detected smoke in the plane's lavatory, as well as a fault in two of the plane's cockpit windows in the final moments of the flight.
France opened a criminal investigation into the disaster in June.
Isis has carried out several attacks in recent years, mainly in the Sinai, where it is based, but also on the Egyptian mainland.
The group claimed responsibility for a suicide bombing at a Cairo church on Sunday, which killed at least 24 people, mainly women, and wounded nearly 50.
In recent months Egypt has spent millions of dollars trying to restore international confidence in its airport security measures.
Russia had suspended all flights to Egypt after the October crash, while Britain cancelled flights to Sharm El-Sheikh, the Red Sea resort from which the airliner took off.