The French bank Société Générale, facing persistent questions over how one junior trader could have caused more than $7 billion in losses, acknowledged Sunday that his activities prompted questions from risk managers several times last year, but that the bank never began a wider investigation because his explanations defused any suspicions.
The new details came as the trader, Jérôme Kerviel, 31, spent a second day in police custody, facing questions about what Société Générale asserted was an elaborate, yearlong ruse that involved betting billions of dollars of the bank's money on European stock index futures.
Mr. Kerviel's lawyers denounced Sunday the "media lynching" of their client in recent days and argued that Société Générale "brought the loss on themselves."
In a five-page statement, the bank outlined how it believed Mr. Kerviel combined several different "fraudulent methods" to hide his activity, including using computer access codes of other employees and falsifying documents.
Jean-Pierre Mustier, chief executive of the bank's corporate and investment banking arm, said in a conference call with reporters that the discovery of the $7.2 billion fraud, on Jan. 18, and the unwinding last week of nearly $75 billion worth of risky investments represented "one of the most difficult periods in the history of Société Générale."
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