Swiss bank UBS's French unit was put under formal investigation on Friday in Paris for alleged complicity in suspected illegal business practices in France, a judicial source said.
UBS France is being investigated by the French judiciary on whether it offered potential French clients investments that were allegedly designed to evade taxes.
Three UBS France executives already have been put under investigation, which means under French law there is serious or consistent evidence pointing to implication of a suspect in a crime.
The judicial source, who spoke on condition of anonymity, said an administrator has been designated to look into the bank's business practices and how bonuses are given out.
UBS France CEO Jean-Frederic de Leusse was recently questioned by judges who had to decide whether to formally place the bank under investigation.
Cash-strapped governments around the world are cracking down on tax evasion and money laundering in the wake of the financial crisis.
The issue took on particular importance in France after former budget minister Jerome Cahuzac quit over allegations that he had an undeclared Swiss bank account, which he later acknowledged.