Police investigating alleged fraudulent share-dealings worth billions of euros at Societe Generale have been given more time to quiz a junior trader at the bank.

Prosecutors now have until tomorrow afternoon to either release Jerome Kerviel or bring charges against him after being granted an extra 24 hours of questioning.

Mr Kerviel, 31, is suspected of being the rogue trader the French bank says cost it €4.9 billion (£3.7 billion).

The trader, who has been suspended from SocGen, presented himself to police on Saturday, dispelling reports he had fled the country.

Speaking to journalists today, Paris’ financial prosecutor Jean Michel Aldebert said: “All is going well. He is co-operating and is ready to explain what happened.”

Over the weekend police visited Mr Kerviel’s flat in the French quarters and SocGen’s headquarters, leaving with boxes of documents and computer hard drives in both instances.

The bank claims the trader, who had been employed at SocGen for seven years, had been committing sums worth more than €50 billion (£37 billion), which is higher than the annual French budget deficit.

French president Nicolas Sarkozy has already said the fraud will not affect the “solidity and reliability” of economic conditions in the European country.

“You can’t assimilate an internal problem at Societe Generale, which is the result of a large scale internal fraud, with what has happened in the international financial system and which comes from the US,” Mr Sarkozy, speaking from New Delhi during a state visit to India, said in reference to the global credit crunch.

The news came a week after SocGen admitted it had suffered a €2 billion (£1.49 billion) loss following the collapse of the US subprime market.