The crisis at Société Générale deepened yesterday as police raided the French bank and arrested a second trader in connection with the €4.9 billion (£3.75 billion) losses run up by the rogue trader Jérôme Kerviel.

The 28-year-old trader – already famous for being Mr Kerviel’s last remaining friend on the social networking site Facebook– was detained after detectives had searched his desk in the bank’s trading room at its headquarters outside Paris. He was taken into police custody for questioning and can be held without charge for 48 hours. French media outlets named him as Manuel Zabraniecki.

A SocGen spokesman confirmed the police raid and said that investigators had taken away documents.

Although SocGen insists that Mr Kerviel acted alone, Renaud van Ruymbeke and Françoise Desset, the magistrates leading the inquiry, are seeking to determine whether he had an accomplice.

Mr Zabraniecki has been employed by SocGen since 2002 and works at its share brokerage unit. He has a degree from the Higher School of Management in Toulouse, southwest France, according to his Facebook profile, where he cites his main interest as women. When the scandal erupted in January, Mr Kerviel had 11 friends on his Facebook site. Within days, all but Mr Zabraniecki had removed their names from the site.

Mr Kerviel, 31, has been remanded in custody on charges of breach of trust, fabricating documents and illegally accessing computers. He is alleged to have taken unauthorised positions totalling €50 billion on European futures markets.

The raid – the third at SocGen since the crisis began – came two days before Maître Elisabeth Meyer, Mr Kerviel’s lawyer, is scheduled to ask a court to release him on bail.

The timing raised suspicions amongst his legal team that magistrates were seeking a pretext to keep him in jail using the argument that he could meet an accomplice if he were freed.

Hours before a remand hearing in February, police announced the arrest of Moussa Bakir, an employee of Newedge, a broker part-owned by SocGen. He was released without charge 48 hours later.

SocGen suffered a further blow yesterday when Cohen Milstein Hausfeld & Toll, a New York law firm, filed a lawsuit alleging that the bank had failed to inform American investors about its sub-prime exposure or Mr Kerviel’s dealings. In France, a spokesman for BNP Paribas, France’s biggest bank by market value, dismissed a report that it would detail a bid for SocGen this spring as a “rumour”.

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