A French submarine has located the flight recorders from Air France Flight 447, which crashed over the Atlantic Ocean last year.

All 228 people on board the flight were killed following the incident, with the cause of the crash still unknown.

Investigators have now narrowed the location of the black boxes down to a five kilometre square area on the seabed. However, their depth may yet make them unrecoverable.

“From our information, the naval nuclear submarine has found the zone of the black boxes,” explained French government spokesperson Luc Chatel in an interview with France Info radio.

“We have to be prudent. It’s just the location that’s been found. We now have to see at what depth they are, if they can be recovered.”

The Airbus SAS A330 jet crashed en route from Rio de Janeiro to Paris on June 1st last year.

France’s BEA air-accident investigation bureau began a third undersea search for the cockpit data and voice recorders last month, in the hope of discovering what caused the crash.

Investigators had previously discovered the plane’s airspeed probes had given false readings, but believe other factors must also have contributed.

The latest search involves the use of sonar from the nuclear naval submarine Emeraude, with oceanographers and mathematicians using satellite data on ocean currents to reduce the search area in the Atlantic Ocean by about 90 per cent.

Air France has thus far declined to comment on the latest developments.

To date salvage teams have pulled about 1,000 pieces of debris and 50 bodies from the ocean.

“It would obviously be very good news for everyone, first for the families of the victims of the flight, and then for all of us, because it has been one year that we have been waiting with impatience to find out what really happened on the Rio-Paris flight,” concluded Mr Chatel.