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PARIS - French investigators say data from the two inflight recorders retrieved from the wreckage of the Air New Zealand Airbus A320 that crashed in the Mediterranean has at last been recovered but caution "weeks" may lie ahead before they can issue a report on the disaster.

In a statement, the Bureau d'Enquetes et d'Analyses pour la Securite de l'Aviation Civile (BEA), the French agency responsible for the probe, confirmed on Thursday (Friday NZ time) that the data from the cockpit voice recorder and the digital flight data recorder had been retrieved at the manufacturers of the so-called black boxes, the US hi-tech corporation Honeywell.

What's a black box?

"Work undertaken in the recorder manufacturer's laboratories, with the participation of specialised investigators from the BEA and the NTSB, made it possible to recover the data from the two recorders' memory cards," the statement said.

Investigators at the BEA - the Office of Inquiry and Analysis for Civil Aviation Safety - at Le Bourget on the northern outskirts of Paris are working alongside New Zealand and German investigators as well as officials from America's National Transportation Safety Board (NTSB) and Airbus Industries.

Information teased from the memory cards could give vital clues to the final moments of the A320, which crashed on November 27 while it was on acceptance trials. The plane was due to be handed back to Air New Zealand after it had been leased by the German company XL Airways for two years.

The cockpit voice recorder registers the conversations on the flight deck, while the digital flight data recorder, or DFDR, contains technical records of the craft including speed, altitude and trajectory. In all, the DFDR monitors 88 parameters such as flap position, autopilot mode and others, such as smoke alarms, that are lesser indicators but still a potent source of information.

An official at the BEA later confirmed to the Herald that the agency is striving to produce a preliminary report but warned against unrealistic time pressures.

"Right now we are working hard to issue a preliminary report in the coming weeks, we cannot say exactly when because it takes time," the official said. "It's a very complex issue examining and analysing everything, this takes time." Investigators are likely to meet in Paris next week to take stock of the investigation.

In the days following the crash, French judicial investigators warned the black boxes had been so badly damaged they were unlikely to yield much insight.

Seven men including five New Zealanders were killed when the twin-engined airline crashed off the coast of Perpignan, southwestern France. Only six bodies have been recovered from the wreckage, which is buried in mud some forty metres under the sea. Experts at the Forensic Research Department in Montpellier are expected to meet with judicial officials on January 13 to review the body identification process and decide when to release the remains.