05/23/2016 02:12 EDT | Updated 05/23/2016 02:59 EDT

EgyptAir Crash: French Ship To Join Search For EgyptAir Flight 804's Black Boxes

Questions remain over what caused the Airbus 320 to crash over the Mediterranean, killing all 66 on board.

CAIRO — The French navy said Monday that one of its ships has joined the search for the wreckage of EgyptAir Flight 804, focusing especially on the hunt for its flight recorders, as questions remain over what caused the Airbus 320 to crash over the Mediterranean, killing all 66 on board, including two Canadians.

Five days after the plane crashed, human remains of the victims arrived at a morgue in the Egyptian capital, Cairo, where forensic experts were to carry out DNA tests, according to the head of EgyptAir, Safwat Masalam.

A security official at Cairo morgue said family members had arrived at the building to give DNA samples to match with the remains, which included those of a child. He spoke on condition of anonymity because he was not authorized to brief the press.

It is still unclear what caused the plane to crash, or indeed what happened to the doomed jet in the final minutes before it disappeared off radar at around 2.45 a.m. local time Thursday.

A general view looking out over the Mediterranean Sea from the coastline of Alexandria where about 290 kilometers north, search operations are taking place to locate the wreckage of EgyptAir flight MS840 on May 21, 2016. (Photo: Getty Images)

The head of Egypt's state-run provider of air navigation services Ehab Azmy told The Associated Press that the plane did not swerve or lose altitude before it disappeared off radar, challenging an earlier account by Greece's defence minister.

Azmy, head of the National Air Navigation Services Company, said that in the minutes before the plane disappeared it was flying at its normal altitude of 37,000 feet, according to the radar reading. "That fact degrades what the Greeks are saying about aircraft suddenly losing altitude before it vanished from radar,'' he added.

"There was no turning to the right or left, and it was fine when it entered Egypt's FIR (flight information region), which took nearly a minute or two before it disappeared,'' Azmy said.

According to Greece's defence minister Panos Kammenos the plane swerved and dropped to 10,000 feet before it fell off radar.

Some wreckage already discovered

Greek civil aviation authorities said all appeared fine with the flight until air traffic controllers were to hand it over to their Egyptian counterparts. The pilot did not respond to their calls, and then the plane vanished from radars.

It was not immediately possible to explain the discrepancy between the Greek and Egyptian accounts of the air disaster.

Egypt, which is sending a submarine to search for the flight recorders, has also refuted earlier reports alleging that search crews had found the plane's black boxes — which could offer vital clues to what happened in the final minutes of the flight.

This August 21, 2015 photo shows an EgyptAir Airbus A320 with the registration SU-GCC taking off from Vienna International Airport, Austria. (Photo: AP)

Ships and planes from Britain, Cyprus, France, Greece and the United States are taking part in the search for the debris from the aircraft, including the black boxes. Some wreckage, including human remains, has been recovered already.

The French vessel is equipped with sonar that can pick up the underwater "pings'' emitted by the recorders. It is specialized in maritime surveillance, and rescue and marine police missions.

The 80-meter (262-foot) ship left its Mediterranean home port of Toulon Friday with a crew of 90, including two judicial investigators. The search area is roughly halfway between Egypt's coastal city of Alexandria and the Greek island of Crete, where water is 8,000 to 10,000 feet (2,440 to 3,050 metres) deep.