A Dutch ship towing a high-tech, U.S. Navy listening device was set to troll the Atlantic on Sunday in search of data and voice recorders that investigators say are key to determining what caused an Air France jet to crash in the Atlantic with 228 people on board.
The Navy device, called a "Towed Pinger Locator," or TPL, will try to detect emergency audio beacons, or pings, emitted by Flight 447's black boxes, which could be lying thousands of feet (meters) below the ocean surface.
Without the recorders, it may be impossible to ever know what caused the Airbus A330 to crash several hundred miles off Brazil's northeastern coast on May 31, experts have said.
The TPL has search capacities up to a depth of 20,000 feet (6,100 meters). The first of two devices was towed in Sunday by a Dutch ship contracted by France, said U.S. Air Force Col. Willie Berges, chief of the U.S. military liaison office in Brazil and commander of the American military forces supporting the search operation.
Berges said the TPL would start operating as soon as searchers were sure it would not interfere with a black-box search being conducted in the same area by a French nuclear submarine.
Another Dutch ship carrying a second listening device is scheduled to arrive no later than Monday morning, Berges said.
The ships will tow the TPLs in a grid pattern while 10-person teams watch for signals on computer screens, Berges said.
The search area includes some of the deepest waters of the Atlantic — and in two more weeks the boxes' signals will begin to fade.
In Paris, the head of Airbus' parent company said there was probably more than one reason for the crash.
"In such an accident, there is not one cause," EADS CEO Louis Gallois said in comments released Sunday. "It's the convergence of different causes creating such an accident."
"It's essential for everybody to know what happened and we know that it's not easy. I hope we will find the black box."
Investigators have so far focused on the possibility that external speed monitors — called Pitot tubes — iced over and gave false readings to the plane's computers.
Also on Sunday, an official of the French accident investigation agency, BEA, arrived in the northeastern city of Recife to begin examining some of the debris retrieved from the ocean, Brazilian Air Force Col. Henry Munhoz said.
He said the French investigator would probably begin with some of the larger pieces such as the nearly intact vertical stabilizer that was fished out of the water by Brazilian searchers.
He said he did not know if the BEA would continue analyzing the pieces in Brazil or have them shipped to France.
French Ambassador Pierre-Jean Vandoorne also arrived in Recife on Sunday to be briefed on the search mission, Munhoz said, without providing further details.
The private Agencia Estado news service quoted Vandoorne as saying that the BEA will also be responsible for examining the passengers' personal belongings.
Thus far, there is no evidence of an explosion or terrorist act, just clues that point to systemic failures on the plane. Experts have said the evidence uncovered up until now points to at least a partial midair breakup of the plane.
Military ships and planes that had suspended their search Saturday due to bad weather resumed operations Sunday, Munhoz said.
Coroners have said victims' dental records and DNA samples from relatives will be necessary to confirm the identities of the 16 bodies that have been examined.
Brazilian authorities Sunday revised the number of bodies they have retrieved downward, from 44 to 43, after a re-count. Another six have been pulled from the Atlantic by French ships.