Two Brazilian naval ships have arrived in a remote part of the Atlantic Ocean to start collecting the wreckage of an Air France passenger jet.
The plane, carrying 216 passengers and 12 crew, left Rio de Janeiro on Sunday night bound for Paris, but dropped off the radar a few hours into the flight.
Authorities are baffled by how a modern plane could have plunged out of the sky without giving its team of three experienced pilots time to send a mayday call.
Air France and government ministers have said bad weather and turbulence were probably behind the disaster, but have refused to rule out other causes, including terrorism.
Wreckage was first found 650km off Brazil's coast, and four more clusters along with a 20km oil slick have been spotted 90km away. The objects were spread across a 5km area, including one metallic object 7 metres in diameter.
French aviation officials say they may never find the plane's flight data recorders, which could be under waters 3,700 metres deep.
Aerial searches have not reported bodies but Brazil's air force has seen more, and larger, debris.
Brazilian Defence Minister Nelson Jobim said the presence of oil slicks could eventually rule out the possibility of a fire or explosion on the plane.
Eleven aircraft have now been sent to the area, about 1,100km north-east of Brazil's coast.
Warning 'black boxes' may never be found
France's minister responsible for transportation, Jean-Louis Borloo, warned that "black boxes" had never been recovered at such depths as the sea currents were powerful that far down.
Paul Louis Arslanian, head of France's air accident investigation agency, said: "We cannot rule out that we will not find the flight recorders."
While the flight recorders were designed to send homing signals for up to 30 days after hitting water, there was no guarantee they even survived the impact, he said.
France held a ceremony for relatives and friends of those on the plane at Notre Dame Cathedral in Paris on Wednesday, attended by President Nicolas Sarkozy.