Debris recovered from the Atlantic by Brazilian search teams does not come from a lost Air France jet, a Brazilian air force official has said.
Flight 477 was carrying 228 people from Rio de Janeiro to Paris and dropped off the radar a few hours into its flight over the ocean on Sunday.
Experts have been mystified by the sudden crash of a modern airliner operated by three experienced pilots, with theories on the cause ranging from extreme turbulence to a loss of cabin pressure to possible computer system faults.
Brigadier Ramon Borges Cardoso contradicted earlier reports that debris had been found, saying "no material from the plane has been recovered".
A wooden cargo pallet was taken from the sea off Brazil's northeastern coast, but the Airbus A330 had no wooden pallets on board.
However, he says he is confident other pieces of debris spotted in the Atlantic are from the missing plane.
Relatives have been told that there is no hope of survivors being found.
Air France chief executive Pierre-Henri Gourgeon and chairman Jean-Cyril Spinetta briefed the passengers' relatives in a hotel near Paris Charles de Gaulle airport where they have been waiting for news.
Mr Gourgeon said the jet broke apart either in the air or when it hit the sea.
In Rio de Janeiro, hundreds of people gathered at a memorial service attended by the French and Brazilian foreign ministers.
"Those who are missing are here in our hearts and in our memories," said the French minister, Bernard Kouchner.
A memorial service was held in Paris on Wednesday.
Oil slick thought to be from ship
Brazilian navy vessels have been combing the area, about 1,100km northeast of Brazil's coast.
Three more Brazilian boats and a French ship equipped with small submarines are expected to arrive in the area in the next few days.
Brigadier Cardoso said that fuel found in the sea probably did come from the plane, because it was not of a type used in ships.
However, he said a large oil slick photographed in the area was more likely to have come from a ship.
He said the search effort would continue, with the main focus on finding bodies, but bad weather is forecast for the region on Friday.