All accusations against licensees shall be filed with the bureau within two years after the performance of the act or omission alleged as the ground for disciplinary action; provided, however, that the foregoing provision shall not constitute a defense to an accusation alleging fraud or misrepresentation as a ground for disciplinary action. The cause for disciplinary action in such case shall not be deemed to have accrued until discovery, by the bureau, of the facts constituting the fraud or misrepresentation, and, in such case, the accusation shall be filed within three years after such discovery.