What laws did he break?

All the news outlets are full of stuff about the French bank trader, Jerome Kerviel. The French police are looking for him in relation to fraud. What I don’t understand is how he is supposed to have been fraudulent? The reports say he didn’t get any of the £3.5 Billion he lost on the markets for himself. How is this fraud? Surely it’s just a case of someone being very, very bad at their job. He should be fired. So should the people he reports to in the bank for letting it happen. When does being crap at your job become a police matter? Am I missing something here?

Update: Apparently he is being questioned about “fraudulent recording of banking records”. Which is probably fair enough. Given that the money is the savers and investors and not the banks, employees probably have a duty of care to safeguard it.