PARIS – France wants to launch an expanded international effort to find the missing wreckage and flight recorders of the Air France jet which crashed in the Atlantic in June, the country's top crash investigator said on Monday.

Around a thousand fragments of the Airbus A330 which crashed on June 1, killing 228 people, have been examined but most of the aircraft is still missing and it is still too early to say definitely what caused the crash, he said.

We are going to see how we can optimize our search. We are going to expand it to other countries to bring in the maximum international dimension and seize every chance we can to avoid missing new clues, Paul-Louis Arslanian, director of France's BEA air crash investigation board, told journalists.

European planemaker Airbus is expected to help fund the move, which could cost several tens of millions of euros, he said, adding an announcement could be made in the autumn.

The United States, Brazil, Britain and Germany are among the nations likely to take part, he said at a specialist briefing.

Authorities have been combing an expanse of ocean the size of Switzerland in a fruitless bid to find the voice and data recorders and the bulk of the plane, which plummeted some 30,000 feet in four minutes before crashing in an equatorial storm.

After failing to pick up radio tracking signals that the recorders were designed to emit for around 30 days, investigators took up the search using a French survey vessel, sonars and submarine but the black boxes are still missing.

The third phase would involve sending sonars or robots to the relatively unexplored seabed, up to 4,000 meters below the surface.

Flight AF447 crashed near the equator while en route to Paris from Rio de Janeiro.

Authorities have found wreckage including the vertical tail and 51 bodies, but are unsure exactly where the crash happened because winds and currents quickly dispersed the debris.

The work is a bit like crossing Switzerland by foot, trying firstly to listen out for the noise of a cricket and now looking for debris with a pocket torch in the dark, Arslanian said.

Speculation on the cause of the crash has focused on the aircraft's speed sensors after error messages suggested inconsistent data readings. But Arslanian said it was still too early to tell if the so-called Pitot probes were to blame.

The full investigation could last over a year, he said.

(Reporting by Tim Hepher and Matthias Blamont; editing by Andrew Roche)

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