Distributing agencies shall investigate promptly complaints received in connection with the distribution or use of donated foods. Irregularities which are disclosed shall be corrected immediately. Serious irregularities shall be promptly reported to the Department. Distributing agencies shall maintain or file evidence of such investigations and actions. The Department also reserves the right to make investigations and shall have the final determination as to when a complaint has been properly handled. Complaints alleged on the basis of race, color, national origin, age, sex or handicap shall be handled in accordance with Sec. 250.21.