Every witness who shall appear before the department by its order shall receive for his attendance the fees and mileage allowed by law for witnesses in civil cases in courts of record, which shall be audited and paid by the state in the same manner as other expenses of the Department of Revenue are audited and paid, upon the presentation of the proper vouchers sworn to by such witness and approved by the department; but witnesses summoned by parties other than the department shall be paid by parties causing the witnesses to be summoned.