French crash investigation advancing: official

PARIS/SAO PAULO (Reuters) - French investigators are getting closer to understanding the cause of an Air France crash that killed 228 people, but difficult search conditions in the Atlantic Ocean are hampering the process, France's chief air disaster investigator said on Wednesday.

The Airbus 330 crashed into the sea en route from Rio de Janeiro to Paris on June 1, killing all on aboard.

The French military is using a mini-submarine to search the sea for the "black box" data and voice recorders which may offer clues to the cause.

"We are getting a little closer to our goal but don't ask me what the percentage of hope is," Paul-Louis Arslanian, head of the French BEA agency in charge of investigating the crash, told a news conference without giving details of its progress.

He said the remote location and uneven surface of the ocean where the search was focused posed one of the biggest challenges in the air crash investigation. The uneven ocean floor means the wreckage could lie anywhere between a depth of 1 km (0.6 miles) and 4 km (2.5 miles).

The BEA has said data transmitted from the plane before it crashed indicated unreliable speed readings from the aircraft's sensors, but cautioned it was too early to say whether this contributed to the accident.

Locator beacons known as "pingers" on the flight recorders send an electronic impulse every second for at least 30 days. The signal can be heard up to 2 km (1.2 miles) away.

"The goal is to understand what happened and for that we need tools and these tools must be facts. The recorders are recorders of facts. If we had them we would have more facts at our disposal," Arslanian said.

ONE PATHOLOGIST NOT ADMITTED

Arslanian said he was unhappy that a pathologist from the BEA had not been allowed by the Brazilians to take part in autopsies on the 50 bodies recovered so far despite his experience examining air crash fatalities.

Brazilian sources and a French diplomat in Brazil said that four other French experts had been authorized to take part in the investigations as observers. The diplomat said the Brazilians wanted to keep a restriction on numbers admitted.

"There are several pathologists and some have been allowed into the Legal Medical Institute but it wasn't possible for everyone to come in. That is what happened," the diplomat, who asked not to be named, told Reuters.

Almost equal numbers of French and Brazilian passengers died in the crash of the Airbus A330, and both countries have been keen to show they are doing their utmost to recover bodies and understand the causes of the disaster.

Arslanian urged the public to show "a lot of patience" and to stick to known facts rather than engage in speculation.

(Writing by Francois Murphy, Estelle Shirbon and Peter Murphy; editing by Stuart Grudgings and Frances Kerry)