An Air France plane that crashed into the Atlantic off Brazil hit the water intact and at high speed, French investigators have said.

Flight AF 447, with 228 people on board, was not destroyed in mid-air during a flight from Rio de Janeiro to Paris on June 1, said Alain Bouillard, who is leading the probe on behalf of France's BEA air accident board.

He said: "The plane was not destroyed while it was in flight. It seems to have hit the surface of the water in the direction of flight and with a strong vertical acceleration."

Mr Bouillard said the pilots of the Airbus A330 attempted to connect to a data system in the Senegalese capital Dakar, three times, but had failed.

Dakar said it had never received the flight plan.

"This is not normal," Mr Bouillard said, adding that investigators also want to establish why it took six hours after the plane disappeared before an emergency was declared.

A search will continue for the missing flight recorders, or black boxes, until July 10, he said - they emit a signal for a limited time.

Mr Bouillard also reiterated that France has not yet been granted access to autopsy reports on bodies taken to Brazil.

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