What are the different tools used for identifying suspicious transactions?

Mr. Karim, a cloth merchant, is maintaining a current account with your branch. At the time of opening the account he declared that he would transact on an average Tk. 5,00,000 daily from his business. However, it is observed that his transaction is Tk. 20,00,000 to 25,00,000. As a banker how would you act in this situation and how would you report the matter to the Bangladesh Bank?