Egypt's head of forensics has denied reports of a possible explosion on board the EgyptAir plane that crashed in the Mediterranean, killing all 66 people on board.

The Associated Press news agency had reported earlier on Tuesday, quoting an unnamed Egyptian forensics official, that human remains retrieved from the plane's wreckage pointed to an explosion on board, even though no traces of explosives had been detected.

The official based his assessment on the small size of body parts so far recovered from the area where flight 804 crashed on Thursday while en route from Paris to Cairo.

"The size of the remains points towards an explosion, the biggest part was the size of a palm," the forensics official said.

The official said about 23 bags of body parts had been collected since Sunday.

However, another senior forensics official said only a tiny number of remains had arrived so far and it was too early to specify whether or not there had been an explosion aboard.

French investigators say the airliner sent a series of warnings indicating that smoke had been detected on board as well as other possible computer faults shortly before it disappeared.

The signals did not indicate what may have caused smoke, and aviation experts have said that neither deliberate sabotage nor a technical fault could be ruled out.

Investigators rely on debris, bags and clothes as well as chemical analysis to detect the imprints of an explosion, according to people involved in two previous investigations where deliberate blasts were involved.

A day earlier, the head of Egypt's state-run provider of air navigation services said that flight 804 did not swerve or lose altitude before it disappeared off radar, challenging an earlier account by Greece's defence minister.

In a search for clues, family members of the victims arrived on Tuesday at the forensics department of the Cairo morgue to give DNA samples to help identify the remains of their relatives.

Egypt has dispatched a submarine to search for the flight's "black boxes" and a French ship joined the international effort to locate the wreckage and search for the jet's data recorders.