The City Auditor shall examine all payrolls, bills and other claims against the City and shall issue no warrant for payment unless he finds that the claim is in proper form, correctly computed and duly approved; that it is legally due and payable; that an appropriation has been made therefor which has not been exhausted; and that there is money in the Treasury to make payment. He may investigate any claim and for that purpose may summon before him any officer, agent or employee of the City, any claimant or other person, and examine him upon oath or affirmation relative thereto, and if he find a claim to be fraudulent, erroneous, or otherwise invalid, he shall not issue a warrant therefor.