Deep water searches for the wreckage and black boxes of of EgyptAir Flight 804 will start in the coming days, according to France's air safety agency.

The BEA said two of its investigators were on board the French navy surveillance vessel La Place, which set sail from Corsica yesterday.

It is working alongside the Egyptian authorities to investigate the crash, which killed all 66 passengers and crew on board the Paris to Cairo flight on May 19th.

The French vessel is equipped with three deep-water devices known as Detector 6000s that can detect the Airbus A320's black box signals, the French agency said.

The Egyptian authorities "will be piloting these underwater searches" with the BEA's help, it added.

Talks are still under way to add a second vessel equipped with a deep-sea exploration robot and the recovery capabilities required to work at an estimated depth of 10,000ft to the mission.

Meanwhile, Airbus has refused to comment on reports that signals from one of the plane's emergency locator transmitters had been detected in the Mediterranean Sea.

Signals from the device, which is activated on impact, would potentially reduce the search area to around 5km.

The plane has three of the transmitters - one of them in the tail near the "black box" flight data recorders.

The signals from the transmitters are different from the "pings" emitted by the black boxes - which record flight data and voices in the cockpit.

Some debris from the plane - including life vests, passenger belongings and pieces of wreckage - has been found, but the fuselage and black boxes are still missing.

Egyptian authorities have said they believe terrorism is a more likely explanation than equipment failure, and some aviation experts have said the erratic flight reported by the Greek Defence Minister suggests a bomb blast or a struggle in the cockpit.