The commissioner has power to require any person engaged in such production and the agent or employee of such person, or purchaser of such oil or gas, or the owner of any royalty interest therein to furnish any additional information the commissioner deems to be necessary for the purpose of correctly computing the amount of said tax, and to examine the books, records, and files of such person, and has power to conduct hearings and compel the attendance of witnesses, the production of books, records, and papers of any person, and full authority to make any investigation or hold any inquest deemed necessary to a full and complete disclosure of the true facts as to the amount of production from any oil or gas location, or of any company or other producer thereof, and as to the rendition thereof for taxing purposes.