The Airbus A400M troop and cargo plane crashed shortly after takeoff outside Seville on Saturday, prompting four nations to ground the plane and France to limit its use to essential operations. Spain also withdrew permission for flight tests.

A safety investigation is being led by Spain's military air crash investigation agency, CITAAM, but the plane's 'black box' recorders have been sent to France where specialist military technicians are helping to extract the data on Spain's behalf.

"We are trying to have some elements as soon as possible, especially as we are using the A400M operationally," the French military official said, asking not to be identified.

"For the moment, we don't have anything that would allow us either to lift the flight restrictions or to make any other recommendations; we have not yet advanced to that point," he said, adding: "We hope to get there within the next 48 hours."

The A400M was equipped with two flight recorders similar, but not identical, to those used for commercial planes: one capturing cockpit voice recordings and the other instrument data that could demonstrate whether the plane had technical problems.

The recorders were recovered from the wreckage on Sunday.

But there have been delays in deciphering the flight data recorder because of problems of compatibility between the recent model and retrieval systems at government-owned laboratories southwest of Paris.

The official said the cockpit voice recordings appeared to be in a usable condition and there was no reason to think that the data could not also be extracted successfully.

"The problem is being resolved," he said.

Airbus and the defence ministry declined to comment.

The read-out is being carried out on CITAAM's behalf by BEAD-air, a French military agency responsible for investigating accidents whenever government-owned aircraft are involved.

The French and Spanish agencies had already co-operated earlier this year on the crash of a Greek F16 fighter in Spain.

BEAD-air is independent from France's better-known BEA, which carries out investigations of civil air accidents.

The head of French avionics firm Thales (>> THALES) said earlier it was ready to provide technical support.

(Reporting by Tim Hepher; editing by Susan Thomas)

By Tim Hepher