PARIS, France (CNN) -- Concerns over the trading carried out by Jerome Kerviel, the trader accused of causing a $7.2 billion loss at Societe Generale, were raised as early as last November, a British newspaper reported Tuesday.
London's Financial Times reported that the Eurex derivatives exchange raised concerns about Kerviel's trading positions near the end of last year. Prosecutors did not specify just who was alerted by Eurex, the paper reported.
Even so, if the reports are true it will put more strain on the management of Societe Generale -- already under pressure to explain why the staggering loss was allowed to go unnoticed for so long.
The Autorite des Marches Financiers -- the French financial market regulator -- said Tuesday it has begun to investigate the bank. Spokeswoman Christine Anglade would not be drawn on the direction of the probe or whether it was related to Kerviel.
Also Tuesday, the French prosecutor who sought charges against trader Kerviel said he plans to appeal a judge's decision to throw out a charge of fraud.
Judge Renaud Van Ruymbeke on Monday filed preliminary charges of abuse of confidence and illegal access to computers against the 31-year-old trader, but he did not agree to charge Kerviel with fraud.
Paris prosecutor Jean-Claude Marin said he plans to appeal the judge's ruling to a higher court, which could reinstate the fraud charge.
The abuse of confidence charge could bring a maximum sentence of three years in prison, lawyers have said, because it is a non-aggravated charge. Had the charge been aggravated, it would have brought a maximum of seven years behind bars.
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The judge freed Kerviel under judicial control after Monday's hearing. Kerviel's lawyers have not said where their client is now. Societe Generale Bank announced last week that Kerviel was responsible for the massive fraud at the bank.
It said he had exceeded his trading limits and made fraudulent transactions involving European index futures. The bank and Marin have said they believe Kerviel acted alone.
But French President Nicolas Sarkozy said Monday that the bank's management had to take responsibility for its acts, indicating he wants the bank's board to take strong action against senior management when it meets Wednesday.
French Finance Minister Christine Lagarde has said she wants the board to decide the fate of bank Chairman and Chief Executive Daniel Bouton. The bank's shareholders have filed a legal complaint seeking to find out what role Societe Generale may have played in the fraud.
Marin said Kerviel told investigators he knew he was doing wrong, but that his actions were no different from those of other traders. Kerviel said he simply got in over his head, Marin added.
Also Tuesday, BNP Paribas said Kerviel's brother, Oliver Kerviel, was forced to resign last year from his position as a portfolio manager. The bank, France's largest, did not give a reason. E-mail to a friend
CNN's Jim Bittermann contributed to this report.