The Auditor shall not allow the amount set aside for any appropriation to be overdrawn, or the amount appropriated for one item of expense to be drawn upon for any other purpose, unless sufficient funds shall actually be in the City Treasury to the credit of the fund upon which such voucher is drawn.  When any claim is presented to the City Auditor, he may require evidence that such amount is due, and for this purpose may summon any agent, clerk or employee of the City, or any other person, and examine him upon oath or affirmation concerning such voucher or claim.  (ORC 733.13)