The EgyptAir passenger jet which crashed into the Mediterranean had "We will bring this plane down" written on its underside, it has been reported.

According to the New York Times, in an eerie coincidence, the plane was once the target of political vandals, who apparently scribbled the graffiti about two years ago.

The EgyptAir security officials said the threatening graffiti had been the work of aviation workers at Cairo Airport who were disgruntled about the domestic Egyptian political situation at the time, the newspaper reported.

Submarine heading for crash site

In a separate development, Egypt's president said a submarine belonging to the country's Oil Ministry had been sent to the site of the crashed jet in the eastern Mediterranean to help search for the cockpit voice and flight data recorders, known as black boxes.

The submarine can operate at a depth of 3,000 metres (9842 feet) below the surface.

Flight MS804 crashed into the Mediterranean on Thursday morning with 66 people on board.

On Saturday French investigators said smoke was detected in multiple places on the plane before it vanished off radar and crashed.

The first pictures of the wreckage recovered from the sea were also released.