PARIS (Reuters) - A deep-sea search for the wreck of an Air France plane that crashed into the Atlantic last year, killing all aboard, has been extended to cover a broader expanse of ocean, investigators said on Tuesday.
Air France flight AF447 between Rio de Janeiro and Paris plunged into a remote corner of the Atlantic during a storm on June 1, killing 228 people.
Although some of the wreckage was subsequently picked up from the sea surface, authorities failed to recover the black box flight recorders and investigators say they need to find them if they are to work out what went wrong with the plane.
Two sophisticated salvage vessels, using miniature submarines, have been scouring a 3,000-square km (1,860-square-mile) area to try to locate the flight recorders of the Airbus A330 plane, but without success.
The mission was due to end at the weekend, but the French air accident investigation authority (BEA) said on Tuesday the search would continue until May 25.
"The BEA believes that it is in fact still possible to localize the airplane wreckage in or near the zone that has just been explored," it said in a statement.
Air France and Airbus had agreed to pay $1.5 million euros each to finance the extension, the BEA said.
Speculation about the cause of the crash has focused on possible icing of the aircraft's speed sensors, which appeared to give inconsistent readings seconds before the plane vanished.
But investigators need to recover the flight recorders to confirm or deny that theory.
(Reporting by Sudip Kar-Gupta; editing by Crispian Balmer and Mark Heinrich)