UBS has been placed under formal investigation for alleged complicity in suspected illegal sales practices, said the French prosecutor's office on Friday. The Swiss bank said it would continue to cooperate with the French authorities.
The move by the French justice authorities comes a week after a probe into the bank's French business.
Under investigation is whether UBS offered potential French clients investments that prosecutors allege were designed to evade taxes. This happened in the early 2000s, a source quoted by the AFP news agency said.