RECIFE, Brazil - The urgent hunt for the black boxes of Air France Flight 447 received a boost yesterday - a French nuclear submarine scoured the search area, listening for the pings of the cockpit data and voice recorders before they fade away.

Brazilian searchers in charge of recovering floating bodies and debris said the surface search area had widened into Senegalese waters. Ocean currents have pushed the remnants far and wide since the Airbus A330-200 went down May 31 with 228 people on board.

The black boxes provide the best hope of unraveling why the jet apparently broke up in midair and plunged into the Atlantic.

With more punishing ocean storms hitting the area as early as today and the possibility that the boxes could have come to rest amid jagged underwater mountains, finding them is a formidable task.

"There are big uncertainties about the accident site, the ocean floor is rugged ... so it's going to be very difficult," French armed forces spokesman Christophe Prazuck told France-Info radio. "It's going to be very complicated, and we're going to need a lot of luck."

The nuclear sub Emeraude plans to trawl 13 square miles a day, using sonar to try to pick up the boxes' acoustic beacons. The submarine will be reinforced by two U.S. underwater audio devices capable of picking up signals even at a depth of 20,000 feet.

If the boxes are located, the Emeraude will launch the unmanned mini-sub Nautile, which had a key role in the search for the wreckage of the Titanic, to recover them.

The first of the two U.S. pinger locators should reach the search area by Sunday. Each one will be slowly towed in a grid pattern while 10-person teams watch for signals, U.S. Air Force Col. Willie Berges said.

A total of 41 victims' bodies have been recovered so far and are being flown to Recife, where investigators hope to identify them and uncover clues based on their injuries.

Prazuck told Associated Press Television News that a French frigate, the Ventose, had already gathered 130 pieces of debris, big and small.

Investigators have focused on the possibility that external speed monitors, called Pitot tubes, iced over and gave false readings to the plane's computers as it flew into thunderstorms.

Airlines around the world have begun replacing Pitot tubes on their aircraft.