BEA director Paul-Louis Arslanian has warned that the investigation will be 'long and difficult' and the failure to find the flight recorders has complicated the probe.
Still, investigators have been scrutinizing some 600 pieces of debris recovered from the crash zone for any clue as to what brought down the plane as it flew through turbulence over the Alantic.
Autopsies were being performed on 51 bodies pulled from the disaster area, some 1,000 kilometres off Brazil's coast.
Brazil decided on June 27 to call off the recovery operation but France has maintained its nuclear submarine, research vessel and other boats in the area on a final hunt for the black boxes.
The homing beacons on the flight recorders emit signals for about one month after the crash and the BEA hopes that they will have a longer-than-usual shelf life.
Search and rescue efforts have been hampered by the fact that the crash zone has ocean depths of up to 6,000 metres.
People from 32 different countries - including 72 French citizens and 59 Brazilians - were aboard the Airbus A330. -- AFP