Flight AF 447 from Rio de Janeiro to Paris crashed on June 1, killing all 228 people on board. Only a small amount of wreckage from the Airbus A330 and fewer than a quarter of the bodies have been recovered.
The Bureau d'Enquetes et d'Analyses (BEA), which is in charge of the investigation into the crash on the French side, said a ship and two submarines were still searching the presumed zone of the crash for the black boxes or flight recorders.
As the flight recorders have now stopped emitting signals, it is necessary to first identify the location of the debris of the plane, and then to search it for the recorders, the BEA said in a statement, explaining that search methods had been adapted.
The BEA said it had noted a pledge by Airbus to help finance a wider search, should it become necessary, but gave no further details.
Citing Airbus Chief Executive Tom Enders, French business daily La Tribune said the company would spend some 12-20 million euros ($17-28 million) over at least three months to support the public investigation into the crash.
The extra financing would allow investigators to extend the search beyond an August 22 deadline and use two or three boats as well as at least one mini-submarine, the newspaper said.
It said Airbus still hoped to find the black boxes, which in some other cases had been found months after a crash.
Evidence from recovered wreckage indicates the plane was broken apart by impact with the water, which it struck facing downwards.
(Reporting by Sophie Hardach and Estelle Shirbon, Editing by Elizabeth Fullerton and Ingrid Melander)