Wis. Stat. § 281.96: Visitorial powers of department.

Every owner of an industrial establishment shall furnish to the department all information required by it in the discharge of its duties under subch. II, except s. 281.17 (6) and (7). Any member of the natural resources board or any employee of the department may enter any industrial establishment for the purpose of collecting such information, and no owner of an industrial establishment shall refuse to admit such member or employee. The department shall make such inspections at frequent intervals. The secretary and all members of the board shall have power for all purposes falling within the department’s jurisdiction to administer oaths, issue subpoenas, compel the attendance of witnesses and the production of necessary or essential data.