No warrant for the payment of any claim shall be issued by the City Auditor unless such claim shall be evidenced by a voucher approved by the head of the department for which the indebtedness was incurred, and countersigned by the City Manager. Before issuing such voucher the supplies and materials delivered, or work done, shall be duly inspected and certified to by the head of the proper department or office, or by a person designated by him. The head of each department or office shall require proper time reports for all services rendered, to be certified by those having cognizance thereof, to serve as a basis for the preparation of payroll vouchers. Each head of a department and his surety shall be liable to the City for loss or damage sustained by the City by reason of the neglect or corrupt approval of any claim against the City, in his department. Prior to drawing of a warrant for the payment of any voucher or claim, the City Auditor may, at his discretion, cause an investigation or
inspection to be made, by a person designated by him, and shall have power to summon persons and examine them under oath or affirmation, which oath or affirmation he may administer.