A signal has been detected that is likely to be from one of the black boxes of the EgyptAir plane that crashed in the Mediterranean last month, Egypt said Wednesday.

The signal was picked up by a French navy ship that is searching for the wreckage of the Airbus A320 using devices to listen for the pings of its flight recorders, the ministry of civil aviation said.

The plane went down with 66 people on board on May 19 during a flight from Paris to Cairo.

Another vessel sent by a private company hired to help find the black boxes is on its way to the area carrying robots that can dive to the seabed to recover them.

The ship is due to arrive at the site within a week, the ministry said.

"Extensive search efforts are being carried out to locate the two data recorders in preparation for their retrieval," the ministry said.

The black boxes, which have enough battery power to emit signals for four or five weeks, could help investigators determine the reason for the crash.

Investigators have said it is too soon to determine what caused the disaster although a terror attack has not been ruled out.

France's aviation safety agency has said the aircraft transmitted automated messages indicating smoke in the cabin and a fault in the flight control unit minutes before disappearing from radar screens.

Meanwhile in PARIS, French investigators confirmed Wednesday, a French naval ship has detected a signal from one of two black boxes belonging to the doomed EgyptAir flight.

"The signal from a flight recorder has been detected" by the survey ship Laplace, said Remi Jouty of France's Bureau of Investigations and Analysis (BEA), following the announcement from the Egyptian authorities.

Jouty said the signal was spotted after data analysis, and a priority search area had been established.

"The detection of this signal is a first step," he said.

The Laplace arrived in the crash zone on Tuesday to join the search for wreckage and the black boxes.

It is equipped with three devices capable of picking up the sonar "pings" from the black boxes at a distance of up to five kilometres (3.1 miles).

The flight recorders could help solve the mystery of why the Airbus A320 plunged into the sea with 66 people on board.