Brazilian authorities released images of the pallet they later called "sea trash"
Debris recovered from the Atlantic by Brazilian search teams is "sea trash" and not from a lost Air France jet, a Brazilian air force official has said.
Brig Ramon Borges Cardoso contradicted earlier reports, saying "no material from the plane has been recovered".
Teams found buoys and a wooden pallet and spotted a fuel slick, and are now searching for an airline seat and a chunk of metal seen earlier this week.
Relatives have been told that there is no hope of survivors being found.
In Paris, Air France Chief Executive Pierre-Henri Gourgeon and Chairman Jean-Cyril Spinetta briefed passengers' relatives in a hotel near Charles de Gaulle airport where they have been waiting for news.
Mr Gourgeon said the Airbus A330 jet, which was carrying 228 people from Rio de Janeiro to Paris, broke apart either in the air or when it hit the sea.
Friends and relatives gathered for a memorial service in Rio de Janeiro
"What is clear is that there was no landing," said a support group representative who was at the meeting.
"There's no chance the escape slides came out," Guillaume Denoix de Saint-Marc said.
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," French minister Bernard Kouchner told mourners.
A memorial service was held in Paris on Wednesday.
Speaking in Recife, the north-eastern Brazilian city from where search operations are being co-ordinated, Brig Cardoso sought to clarify earlier declarations that the wooden pallet and fuel slick had come from the Air France jet.
The Airbus A330 was not carrying wooden pallets, it was reported, while a large slick spotted in the area most likely spilled from a ship rather than from a downed plane.
Other fuel found in the sea probably did come from the Airbus, he said.
"It has been verified that the material did not belong to the plane, they were wood pallets that were used by ships and sometimes planes, but in this flight to Paris, there were no wood pallets," Brig Cardoso said.
Navy ships are now reported to be scouring the surface of the ocean, about 1,100km (690 miles) north-east of Brazil's coast, in an effort to locate other debris spotted from the air during the first sweeps of the area on Tuesday and Wednesday.
Rescuers hold out more hope that what was reported to be a seat and a large chunk of metal could have come from the plane, reports say.
Three more Brazilian boats and a French ship equipped with small submarines are expected to arrive in the area in the next few days.
He said the search effort would continue, with the main focus on finding bodies, but bad weather is forecast for the region on Friday.
French military spokesman Christophe Prazuck said the priority was looking for wreckage from the plane, before turning the search to flight data recorders.
"The clock is ticking on finding debris before they spread out and before they sink or disappear," he said.
French officials have said the recorders, which could be deep under water, may never be found.
Officials have warned that they are far from working out the cause of the crash.
Investigators are reported to be relying on a stream of automated messages sent out just before the crash, which suggested the plane's systems shut down as it flew through high thunderstorms.
France's air safety investigation agency said on Friday that the messages revealed an "inconsistency in the different speeds measured".
It has been suggested that speed sensors failed or iced over, causing erroneous data to be fed to onboard computers. This might have caused the plane to fly too fast or too slowly through the storm, leading it either to break apart or stall and fall out of the sky.
A Spanish pilot flying in the area at the time of the crash was quoted by his airline, Air Comet, as saying he had seen an "intense flash of white light, which followed a descending and vertical trajectory and which broke up in six seconds".
The paper said Airbus, the maker of the plane, would issue A330 jets with new advice on flying in storms.
Airbus declined to comment on the report, though an unnamed official told AFP news agency that it was normal to update airlines following an accident.