§ 56. Examination of books and accounts. The mayor shall have authority at all times to examine the books and papers of any officer, employee or department of the city and, as often as he may deem proper, to appoint one or more competent persons to examine, without notice, the accounts of any city officer or department, and the money, securities and property belonging to the city in the possession or charge of any officer or department and to report the result of such examination; and he may administer oaths to witnesses and take affidavits in all cases relating to the affairs of the city.