A French nuclear submarine is being sent to help find an Air France jet which disappeared over the Atlantic.
Defence minister Herve Morin said the hunter-killer submarine had surveillance equipment that could help find the plane's flight data recorders.
The Airbus A330 jet vanished over the Atlantic en route from Rio de Janeiro to Paris on Monday with 228 people on board.
As the search continued on Friday, it was revealed that a wooden pallet and a fuel slick in the vicinity of the plane's last known position were not from the jet.
A Brazilian air force official said the slick was most likely from a passing ship.
Navy ships are searching the ocean about 1,100km north-east of the coast of Brazil, for other debris spotted from the air on Tuesday and Wednesday.
A French marine research ship equipped with two non-nuclear mini-submarines is en route to the area.
The BBC reports three more Brazilian boats and a French ship equipped with small submarines are expected to arrive in the next few days.
French officials have said the flight data recorders, which could be deep under water, may never be found.