by Eve Sveftel

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ATTENTION - UPDATES with SocGen statement ///

PARIS, Jan 27, 2008 (AFP) - French investigators on Sunday extended the detention of accused rogue trader Jerome Kerviel over a seven billion dollar fraud as Societe Generale revealed he had been gambling with more than 73 billion dollars in deals when caught.

Kerviel, 31, turned himself in to police on Saturday, two days after Societe Generale said it had lost a staggering 4.9 billion euros (7.15 billion dollars), the biggest in investment banking history.

Prosecutors extended his detention for questioning for another 24 hours. They must now decide on Monday whether to release Kerviel or place him under formal investigation.

"It's going well. The investigation led by the experts from the financial brigade is extremely fruitful," said Jean-Michel Aldebert, head of the Paris prosecutor's office financial division.

Aldebert said Kerviel was providing "very interesting" facts and that he told investigators he was feeling fine.

In a statement, Societe Generale said that the trader had held positions worth about 50 billion euros (73 billion dollars) when he was caught -- a figure well in excess of the bank's market value of 35.9 billion euros.

Quick action was taken to liquidate the deals, limiting losses to 4.9 billion euros, the bank said.

The trader had bought futures in three European indices -- the Eurostoxx, the DAX in Frankfurt and the Footsie in London -- effectively betting on the future direction of the stock market.

Kerviel was taken into custody on Saturday to explain his role in the scandal, which has raised international questions over how one person could have caused such big losses without getting caught earlier.

The case dwarfs that of Nick Leeson, who lost 1.5 billion dollars as a Singapore-based trader at Barings, causing the collapse of the venerable British bank in 1995.

Investigators were seeking to establish the trader's motives, how he allegedly managed to elude detection and whether he acted alone, said a source close to the case.

They were also examining whether he hacked into the bank's computer system.

Police searched the bank's headquarters near Paris on Friday, seizing computer discs from Kerviel's office and on Saturday raided Kerviel's apartment in the wealthy Paris suburb of Neuilly-sur-Seine.

For the past few days, Kerviel had been staying with friends in the Paris region. Police confirmed that he had not been on the run and had agreed to cooperate with investigators.

Societe Generale has filed a criminal complaint against Kerviel, alleging the use of falsified documents and unauthorised computer access.

Kerviel joined Societe Generale's investment banking department in 2000 and moved five years later from the back offices to the front office where he began trading in futures.

Societe Generale chairman and chief executive Daniel Bouton has described Kerviel as a "crook, fraudster and terrorist" but colleagues quoted in the press have portrayed him as a shy, unassuming young man.

Kerviel's family from the small town of Pont L'Abbe in Brittany defended the young man, with his aunt suggesting he is being made the scapegoat for mismanagement or other wrongdoing at the bank.

"Jerome is not capable of doing such a thing," said his aunt Sylviane Le Goff in an interview with RTL radio.

"You have to look around in his entourage, his superiors and management (to find the culprits). Jerome is an honest and serious boy who is close to his family," she said.

Bouton denied in an interview to Le Figaro daily that the bank had tried to hide losses from other bad deals in the Kerviel case.

"What happened at Societe Generale is certainly not a disaster that resulted from our strategy. It is more like an accidental fire which destroys a large factory at an industrial plant," Bouton said.

Bouton has denied suggestions by analysts that the bank might have put losses from other bad deals into the case, which has stunned international markets already reeling from the US subprime mortgage crisis.

Societe Generale has said it also lost two billion euros in subprime deals.

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