PARIS (Bloomberg) - Societe Generale SA's Fimat unit began investigating Jerome Kerviel's trades through broker Moussa Bakir four months before the bank blamed Mr. Kerviel for a record loss.

The head of Mr. Bakir's desk initiated an "internal study" after seeing "an unusual increase" in the commissions the broker received on trades he executed for Mr. Kerviel, Fimat spokesman Jean-Christophe Huertas said.

"In September, they began to see some things," Mr. Huertas said, declining to specify the size of the commission increases.

Societe Generale reported a 4.9 billion-euro ($7.2 billion) trading loss after it liquidated 50 billion euros in unauthorised futures positions Mr. Kerviel amassed and concealed with fake hedges. French judges this month named Bakir a material witness in their investigation into the trades. Mr. Kerviel, 31, passed many of his transactions through Mr. Bakir.

The findings of an initial inquiry, showing that Mr. Bakir got the commissions for cash equity trades executed last summer, were submitted in mid-November to Fimat executives, who decided to start a full investigation, Mr. Huertas said. Fimat was then in the midst of completing a merger with Credit Agricole SA's futures brokerage to form a new entity, Newedge.

"There was some piece of this risk-management function that did work," said Christopher Mesnooh, a Paris lawyer at Hughes Hubbard & Reed, not involved in the case. The inquiry "got lost in the shuffle."

The review "proceeded in complete transparency and all in accordance with the regular procedures of back offices at Societe Generale and Fimat," Mr. Huertas said. The investigation was earlier reported in the Financial Times.

Fimat did not alert Societe Generale to the investigation until after the bank disclosed its trading loss on January 24, Mr. Huertas said. The brokerage did, however, verify the transactions during the inquiry with the client - in this case, Societe Generale - which determined the commissions.

"The conditions are always set by the customer, especially if the customer is the owner," said Stanley Jonas, former managing director in derivative products at Fimat USA, the New York-based unit of French brokerage. "If it was an outside firm, it never would have happened. SocGen ran every detail at Fimat."

The Fimat inquiry marks yet another warning sign Societe Generale missed, raising questions about management oversight at France's second-largest bank. In November, Eurex, Europe's largest futures exchange, queried the bank about the size of Mr. Kerviel's trades. Mr. Kerviel was able to explain away the concerns.

Also, during the course of 2007, Mr. Kerviel took only four days of vacation, telling prosecutors that it should have alerted his managers. "A trader who doesn't take vacation is a trader who doesn't want to leave his book to someone else," he said during his interrogation.

Jean Veil, a lawyer for Societe Generale, said he was looking into the Fimat inquiry, adding that the brokerage and the bank operated as "two different companies." The bank declined to comment on the investigation.

Christophe Reille, a spokesman for Mr. Kerviel, declined to comment on the Fimat investigation. Jean-David Scemama, Bakir's lawyer, did not return messages left at his office and on his mobile phone requesting comment.