A Dutch ship towing a high-tech, US Navy listening device was set to troll the Atlantic on Monday 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, will try to detect emergency audio beacons, or pings, from Flight 447's black boxes, which could be lying thousands of metres 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.
The locator device is capable of searching to a depth of 6,100 metres. The first of two devices was towed in today by a Dutch ship contracted by France, said US Air Force Col Willie Berges, commander of the American military forces supporting the search operation.
Berges said the locator device would start operating as soon as searchers were sure it would not interfere with a French nuclear submarine already searching for black boxes.
Another Dutch ship carrying a second listening device is scheduled to arrive no later than tomorrow morning, he said.
The ships will tow the locators in a grid pattern while 10-person teams watch for signals on computer screens.
The search area includes some of the deepest waters of the Atlantic -- and in two more weeks the boxes' signals will begin to fade.