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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, investigators said on Wednesday.

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

The signals were picked up by French survey ship Laplace which is using acoustic detection systems to listen for the "pings" emitted by the flight recorders, France's aviation safety agency BEA said.

"The detection of this signal is a first step," said BEA official Remi Jouty.

Egypt's ministry of civil aviation had announced the potential breakthrough earlier, saying the signals were "assumed to be from one of the data recorders".

Some of the wreckage has already been pulled from the Mediterranean along with passenger belongings. No survivors have been found.

Another vessel sent by Deep Ocean Search (DOS), a private company hired to help find the black boxes, is on its way to the area carrying a ship with a robot capable of diving up to 3,000 metres (yards) to retrieve the recorders.

The ship is due to arrive at the site within a week, the Egyptian 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 have enough battery power to emit signals for four or five weeks.

Since the crash, small pieces of the wreckage and human remains have been recovered while the bulk of the plane and the bodies of the passengers are believed to be deep under the sea.

A Cairo forensic team has received the human remains and is carrying DNA tests to identify the victims. The search has narrowed down to a five-kilometre (3-mile) area in the Mediterranean.

David Learmount, a consulting editor at the aviation news website Flightglobal, said the black boxes' batteries can transmit signals up to 30 days after the crash. But even if the batteries expire, locating the boxes remains a possibility.

"It's terribly important to find the black boxes, because if they don't find them, they will know nothing about the aircraft," he said, citing a 2009 incident when black boxes were found two years after a crash in the Atlantic Ocean.

Nearly two weeks after the crash off Egypt's northern coast, the cause of the tragedy still has not been determined.

Egypt's civil aviation minister Sherif Fathi has said he believes terrorism is a more likely explanation than equipment failure or some other catastrophic event.

But no hard evidence has emerged on the cause, and no militant group has claimed to have downed the jet. Earlier, leaked flight data indicated a sensor had detected smoke in a lavatory and a fault in two of the plane's cockpit windows in the final moments of the flight.

Agencies contributed to this report