PARIS - THE Air France jetliner that crashed in the Atlantic a month ago with 228 people on board did not break up in mid-air, the French bureau leading the investigation said on Thursday.

'The plane was not destroyed while in flight,' said Alain Bouillard from the BEA accident investigation agency, which released its first report on the June 1 disaster.

'The plane appears to have hit the surface of the water in flying position with a strong vertical acceleration,' he added, explaining that the plane hit the water belly-first.

The crash of Flight 447 from Rio to Paris was the worst in Air France's history.

There had been speculation that problems with the Airbus' airspeed sensors, or pitot tubes, may have caused the plane to stall or fly dangerously fast, causing a high-altitude breakup.

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 BEA lead investigator said the search would continue until July 10.

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.

Investigators have been scrutinising some 640 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. -- AFP