Greek defence officials told Reuters pieces of white and red plastic were spotted close to an area where a transponder signal was emitted earlier.

The discovery came as Egyptian Civil Aviation Minister Sherif Fathy said the plane was more likely to have been brought down by a "terror attack" than a technical fault, 

A search is under way for the jet which disappeared with 56 passengers and 10 crew on board - including one British national.

The fate of the plane is not yet known and officials have said it is too early to rule out any possibility, including terrorism, but all those on board are now feared to have died.

French President Francois Hollande said "unfortunately the information we have ... confirms to us the plane came down and is lost", suggesting it crashed near the southern Greek island of Karpathos where the search is focused.

At the same time, Greek defence minister Panos Kammenos said the aircraft was in Egyptian airspace and flying at 37,000ft when it made "sudden swerves" and plunged to 15,000ft.

He said it swerved "90 degrees left and then 360 degrees to the right" before vanishing.

Authorities are examining CCTV footage at Charles de Gaulle Airport - and investigating an account from the captain of a merchant ship who reported seeing a "flame in the sky" some 130 nautical miles south of Karpathos.

Mr Fathy said there were no known security issues with the passengers who boarded the jet, but further checks were being made.

:: EgyptAir Flight Disappears: Live Updates

Flight MS804 departed the French capital at 11.09pm (CEST). The airline said the plane lost contact with radar at 2.45am Cairo time (1.45am BST). It was last in touch 10 minutes earlier.

At that stage the Airbus A320, which was 13 years old and had logged 48,000 flight hours, was about three hours and 40 minutes into the four-hour journey.

:: EgyptAir Plane: What Could Have Happened?

Military search and rescue teams picked up an automated signal from the plane's emergency beacon at 4.26am Cairo time (3.26am BST) - around 80 minutes after it was supposed to land in Cairo. It is thought this may have been triggered on impact.

Thirty Egyptians, 15 French, two Iraqis, a Belgian, Kuwaiti, Saudi, Sudanese, Chadian, Algerian, Portuguese and Canadian are among the passengers which also include one child and two babies.

Greek and French boats and planes have joined special teams from the Egyptian armed forces in the search for the jet. Greece also has a submarine on standby, while Britain and the US have offered their support too.

RFA Lyme Bay is on its way to the search area and is expected to arrive there later this evening.

Greek civil aviation authorities said the jet disappeared off its radar two minutes after leaving its airspace. Prior to that, its air traffic controllers spoke to the pilot who reported no problems.

However, just before the handover to Cairo airspace, calls to the plane went unanswered.

Ahmed Abdel, the vice-chairman of EgyptAir holding company, told CNN there had been no distress calls from the plane.

The New York Times quoted Ehab Mohy el-Deen, the head of Egypt's air navigation authority, as saying: "They did not radio for help or lose altitude. They just vanished."

The airline said the plane's pilot had flown 6,275 hours - including 2,101 hours on the same model - while the co-pilot had done 2,766 hours.

Commercial airline pilot Chris McGee told Sky News there were only two circumstances that would prevent a pilot from contacting air traffic control: "One would be if there was human intervention. The second is something has occurred on the flight deck."

A crisis centre offering support to the distressed families of loved ones on board has been set up at Cairo International Airport.

Sky's Middle East Correspondent Sherine Tadros, at the airport, said: "People here are in tears and are losing hope as the hours go by."

Source :Skynews