A former Credit Suisse employee surrendered to the FBI on Wednesday on criminal charges, an FBI spokesman said, in a U.S. government probe on writedowns on subprime mortgage derivatives at the height of the financial crisis.

Sources familiar with the investigation said on Tuesday that as many as four former Credit Suisse traders were expected to face either criminal or civil charges and that the Swiss bank will not be charged in the matter.

The FBI spokesman identified the former Credit Suisse employee who surrendered in New York as David Higgs. An attorney for Higgs was not immediately identified. Higgs was scheduled to appear in U.S. District Court in New York on Wednesday.

A spokeswoman for the office of the Manhattan U.S. Attorney declined to comment.

The investigation stems from $2.85 billion in writedowns that Credit Suisse took on collateralized debt obligations in 2008, said the sources, who spoke on the condition of anonymity.

Credit Suisse revealed those CDO losses in early 2008, and blamed them on a group of rogue traders - who the bank said had deliberately mispriced securities - and on a failure of internal controls.

(Reporting By Grant McCool, Basil Katz, Lauren Tara LaCapra, Jennifer Ablan; editing by Mark Porter)