Egyptian search teams have detected an emergency signal from the wreckage of EgyptAir Flight 804, according to the lead investigator.
Captain Ayman Al Moqadem said the detection of the signal by satellite could help his team locate the plane's fuselage on the floor of the Mediterranean Sea.
He said the breakthrough would narrow the search zone for the main body of the aircraft from a 64 kilometre radius to about five, The Wall Street Journal reported.
So far, searchers have only been able to recover parts of human remains, pieces of the wreckage and debris.
EgyptAir Flight MS804 crashed in the Mediterranean last Thursday between the Greek island of Crete and Egypt's north coast with 66 people aboard, including 30 Egyptians and 15 French nationals.
Egyptian investigators said some of the wreckage already found had been sent to a forensic lab for analysis, along with small fragments of human remains for possible identification.
They also said no possible cause for the crash has been ruled out.
The search for the black boxes
Deepwater search operations to locate the wreckage and black boxes of the missing EgyptAir plane will start in the coming days, France's BEA air safety agency said.
"A deep-water search campaign will begin in the coming days with the arrival in the accident area of the French navy surveillance vessel 'La Place'," said the BEA, which is working alongside the Egyptian authorities to investigate the May 19 crash.
France and Egypt will hire two private firms to help in the hunt for the black boxes.
"We are in talks with two private companies ... in co-ordination with the Egyptian authorities," a French ministry spokesman said. "The idea is to mobilise the resources very quickly."
A diplomatic source in Paris said the two companies, both French, were the Mauritius-based Deep Ocean Search and Alseamar, based in the French capital.
French and Egyptian aviation officials have said it is too soon to determine what caused the disaster although a terror attack on the Airbus A320 has not been ruled out.
France and Egypt will share the costs for the search, which faces a race against the clock, as the flight data and voice recorders emit locator "pings" for no more than about a month.
DOS says it can operate in depths of up to 6000 metres (20,000 feet) and has a robot that is capable of mapping the seabed.
Egypt has deployed a submersible that can operate at a depth of 3000 metres in the hunt for the black boxes, while a French patrol boat is also in the search area, concentrating mainly on the surface.
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 before contact was lost.