Search crews are scouring for further wreckage of EgyptAir flight 804 — including for the plane's black boxes, which could provide vital clues to why the jetliner crashed killing all 66 on board.

Planes and vessels from Egypt and five other countries are searching a wide area of the Mediterranean Saturday, a day after the Egyptian army found debris from the Airbus 320 in the sea 180 miles (290 kilometers) north of Alexandria.

No hard evidence has emerged to why the plane dropped off radar, swerved wildly and plummeted early Thursday morning.

Investigators are considering the possibility of a terror attack. No militant group claims to have brought down the plane.

The industry publication Aviation Herald reports that sensors detected smoke in the plane's lavatory, suggesting a fire onboard.