A prosecutor in

Switzerland is pursuing a criminal complaint against a former employee of UBS for allegedly running a Ponzi scam funded by millions of Swiss francs in client funds from the Swiss bank, according to Dow Jones.

The former employee, who has been held in custody since early December, has confessed to taking funds from UBS clients and investing them privately, using new money to pay off existing investors in the scheme, the prosecutor's office in Solothurn said.

The prosecutor is pursuing the former UBS employee and another individual formerly with Raiffeisen Bank on suspicion of misappropriation of funds, money-laundering and falsification of documents. Raiffeisen spokesman Franz Wuerth wasn't immediately available for comment.

Based on initial results from the investigation, the prosecutor's office said it believes roughly 100 investors are involved in the alleged Ponzi scam, but added it is premature to estimate the scheme's financial size.

UBS said the bank terminated the employee's contract without notice in December over "severe violations of labour law," without detailing specifics. UBS spokesman Dominique Gerster declined to elaborate on the prosecutor's statement, the newswire said.