What are the duties of auditor if he notices fraud during the course of audit ?

Under section 143(12) of Companies Act, if an auditor of a company in the course of the performance of his duties as auditor, has reason to believe that an offence of fraud involving such amount or amounts as may be prescribed, is being or has been committed in the company by its officers or employees, the auditor shall report the matter to the Central Government within such time and in such manner as may be prescribed. Provided that in case of a fraud involving lesser than the specified amount, the auditor shall report the matter to the audit committee constituted under section 177 of Companies Act or to the Board in other cases within such time and in such manner as may be prescribed. Provided further that the companies, whose auditors have reported frauds under this sub-section to the audit committee or the Board but not reported to the Central Government, shall disclose the details about such frauds in the Board's report in such manner as may be prescribed.