RECIFE, Brazil - A U.S. navy team was flying to Brazil on Monday with high-tech underwater listening devices to help the search for the black boxes from an Air France plane that crashed into the Atlantic Ocean.

Brazilian and French military ships, which have so far recovered 17 bodies and large amounts of plane wreckage from the sea, resumed their search amid the floating debris.

What caused the Airbus A330 to crash May 31 with 228 people on board will remain a mystery unless searchers can locate the plane's black box flight data and voice recorders, likely buried deep in the ocean. Brad Clemes, 49, of Guelph, Ont., was among the passengers, all of whom are presumed to have perished.

Two U.S. navy devices that can detect emergency beacons to a depth of 6,100 metres were being flown to Brazil with a navy team, according to the Pentagon. They will be delivered to ships that will then listen for transmissions from the black boxes, which are programmed to emit signals for at least 30 days.

Seventeen bodies were recovered Saturday and Sunday about 70 kilometres from where the jet sent out messages signalling electrical failures and loss of cabin pressure.

Authorities also announced that searchers spotted two airplane seats and debris with Air France's logo, and recovered dozens of structural components from the plane. They had already recovered jet wing fragments, and said hundreds of personal items believed to from passengers were plucked from the water.

Brazilian President Luiz Inacio Lula da Silva said his country's military would do all it can to retrieve bodies and return them to relatives.

"We know how significant it is for a family to recover their loved one," Silva said Monday on his weekly radio show. He added: "During this painful time it's not going to resolve the problem, but it is an immense comfort to know they can bury their loved ones."

France is leading the investigation into the cause of the crash, while Brazilian officials are focusing on the recovery of victims and wreckage from Flight 447, which likely broke up in midair in turbulent weather the night of May 31 while en route from Rio de Janeiro to Paris.

There is "no more doubt" that the wreckage is from Air France Flight 447, Brazilian air force Col. Henry Munhoz said Sunday.

French military spokesman Christophe Prazuck said the nuclear attack submarine Emeraude would arrive at the scene later this week and "will try to find the acoustic pings emitted by the black box."

The Ventose, a French military frigate, arrived Sunday and is now under Brazil command, Prazuck said. That ship has found and brought aboard seven of the 17 bodies of victims discovered so far, and about 30 pieces of debris that "most probably come from the plane," Prazuck said.

Another French navy ship, the Mistral, is headed to the site, he said, and the oceanographic survey ship Pourquoi Pas, equipped with deep-water unmanned subs, is also en route and will try to retrieve the black boxes.

The search is focusing on a zone of several hundred square kilometres roughly 640 kilometres northeast of the Fernando de Noronha islands off Brazil's northern coast.

Brazilian authorities have refused to release the precise co-ordinates of where they are looking, except to say the area lies southeast of the last jet transmission, possibly indicating the pilot was trying to turn around in mid-flight and head back to the islands.

The investigation is increasingly focused on whether external instruments on the Airbus A330 may have iced over, confusing speed sensors and leading computers to set the plane's speed too fast or slow - a potentially deadly mistake.

The French agency investigating the disaster said airspeed instruments on the plane had not been replaced as the maker had recommended, but cautioned that it was too early to draw conclusions about what role they may have played in the crash.

The agency, BEA, said the plane received inconsistent airspeed readings from different instruments as it struggled in a massive thunderstorm.

Munhoz and Brazilian Navy Capt. Giucemar Tabosa Cardoso declined to comment on the condition of the bodies, saying that information would be too emotionally painful for relatives.

Neither would authorities immediately identify hundreds of personal items that have been recovered. Relatives of the victims were devastated by an announcement Saturday that a laptop computer and briefcase containing a plane ticket had been found.

"We don't want to cause them more suffering," Munhoz said.

The bodies and plane wreckage were being transported by Brazilian and French ships and should arrive Tuesday at the Fernando de Noronha islands, where the military has set up a staging post for the search operation. From there, remains and debris will be taken to the northeastern coastal city of Recife for identification.

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