Officials in Brazil said search teams had spotted four more clusters of debris about 90 km (55 miles) south of the first wreckage discovered on Tuesday in the middle of the Atlantic.
Brazilian and French ships are heading to the area, some 745 miles (1,200 km) northeast of Brazil's coastal city Recife hoping to retrieve as much of the wreckage as possible.
France is dispatching a mini submarine that can explore to a depth of 6,000 metres (19,680 ft) and will try to locate the Airbus's flight data and voice recorders, which should shed light on a crash that has puzzled aviation experts.
But Paul Louis Arslanian, the head of France's air accident investigation agency, said he was not sure that the black boxes would be recovered and said the probe might prove frustrating.
"I am not totally optimistic. We cannot rule out that we will not find the flight recorders," Arslanian told reporters, warning the inquiry could take a long time to wrap up.
"I cannot rule out the possibility that we might end up with a finding that is relatively unsatisfactory in terms of certainty," he added.
A first report will be ready by the end of the month, with the investigation led by Alain Bouillard, who took charge of the investigation into the crash of an Air France Concorde in 2000.
Arslanian revealed few new elements, confirming only that the crew had sent a radio message reporting turbulence as it headed towards the equator and that the plane had later sent a rapid series of automated messages reporting malfunctions.
"For now, there is no indication to suggest that the plane had a problem before its take off," he said.
Mountainous Undersea Landscape
Brazilian Air Force spokesman Colonel Jorge Amaral said on Wednesday that the newly spotted debris included "various objects" spread across a 5-km area, one metallic object 7-metres in diameter and a 20-km oil slick.
An aviation expert said the large distance between the wreckage zones might be an indication the plane broke up in the sky well before it hit the water.
Brazil has sent four navy ships and a tanker to the remote corner of the ocean, with divers on hand to salvage the pieces.
France dispatched a boat with the Nautile submarine aboard, but it was not expected to reach the zone until early next week.
French government minister Jean-Louis Borloo said the recorders were believed to be at a depth of between 3,660 metres and 3,700 metres, within reach of the submarine, but warned they would be hard to find.
"We have never recovered black boxes that deep before and ... the sea currents are powerful that far down," he said.
Arslanian said the seabed in the area was rugged.
"It is practically in the middle of the Atlantic Ocean where the floor is very deep and varied. It is a mountainous seascape rather than a plain," he said.
The recorders are designed to send homing signals for up to 30 days when they hit water, but there is no guarantee they even survived the impact with the sea, Arslanian said.
France held an ecumenical religious ceremony for relatives and friends of those on the plane at Notre Dame Cathedral in Paris on Wednesday, attended by President Nicolas Sarkozy.
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.
French investigators have divided into four teams to probe various aspects of the case, including a review of the plane's on board systems and maintenance record.
Paris magistrates said they would open an inquiry, a routine procedure following such large loss of life.
