French banker charged
Preliminary charges have been filed against Jerome Kerviel, the trader blamed for huge losses at French bank Societe Generale.
His lawyer said he will be investigated for breach of trust, falsifying documents and breaching computer security - but not for fraud.
Kerviel has been released on bail.
The bank says his actions cost it 4.9 billion euros.
Under French law, a formal investigation does not automatically guarantee that a trial will follow. Breach of trust carries a maximum sentence of three years in prison and a fine of 370,000 euros.