The US Navy has sent two high-tech devices to French ships to aid in locating the black box flight recorders onboard the ill-fated Air France A330 that crashed in the Atlantic Ocean.

The towed pinger locators sent from the US Navy can find emergency beacons to a depth of 20,000ft, according to a senior defence official.

The locators will be placed on to two French tugs, which will use them to listen for transmissions from the black box.

The locators are 5ft long and 5in in diameter and are towed behind vessels at slow speed.