French bank Societe Generale, at the centre of a huge trading scandal, began investigating trades executed by Jerome Kerviel months before his activities were exposed in January, the Financial Times reported.
The FT said it had learnt that a senior executive of Fimat, then a wholly-owned subsidiary of SocGen, began investigating at the end of September deals executed by Fimat employee Moussa Bakir for Kerviel after being alerted to abnormally high volumes on his broking desk.
The Financial Times gave no source for the report.
SocGen declined to comment.
The Fimat executive raised questions about commissions paid to Bakir on at least four cash equities trades for Kerviel.
But he uncovered nothing conclusive and the inquiry was not prioritized as he prepared for Fimat's merger with Calyon Financial that created Newedge, as the company is now known, the newspaper reported.
The investigation was still under way when Socgen discovered in January that Kerviel had separately built up unauthorized futures positions totaling 50 billion euros ($73.43 billion), trying to cover his tracks with faked hedges.
The revelation that there were concerns last autumn that could have led to a wider investigation will be embarrassing for SocGen, said the Financial Times. But it added that it was unclear whether the Fimat inquiry into cash equities trading would have led to an alert sooner within SocGen.
In a separate interview, Bank of France governor Christian Noyer said he was more inclined to blame human error for the fact that Kerviel's massive trades were not spotted rather than a culture of excessive risk-taking.
It was totally outside the policy of the bank to take such large positions, told the Financial Times.
Noyer also defended the central bank's Banking Commission inspectors who made repeated inspections in 2006 and 2007 at Socgen.
We don't pretend we can control everything. It is the internal control that has to do that, he added.
Noyer believed that what happened at Socgen was an aberration, the newspaper said.
We're talking of a classic fraud, he said. There is no 100 percent certainty against fraud.
Many analysts have expressed disbelief that Kerviel's rogue trades, which SocGen blames for losses of 4.9 billion euros ($7.1 billion), could have gone entirely undetected by his supervisors for so long.
French judges on February 9 dismissed conspiracy accusations against Bakir, accused by prosecutors of assisting in the trading by Kerviel which SocGen blamed for the loss.
(Reporting by Andrew Hurst; editing by Rory Channing, Paul Bolding)