The department of agriculture may receive verified complaints from any producer against any commission merchant, dealer, broker, agent, processor, or retail merchant or any person assuming or attempting to act as such and upon receipt of the verified complaint may make any and all necessary investigations relative to the complaint. In conducting any investigation, the department or its authorized agent may examine any ledgers, books, accounts, memoranda, and other documents, farm produce, scales, measures, and any other articles and things used in connection with the business of the person of whom the complaint has been made.