The commission shall investigate the enforcement of this Division and its rules, and the action of examiners herein provided for and the conduct and action of the appointees on the classified civil service of said county. In the course of such investigation each commissioner shall have power to administer oaths, and said commission shall have power to secure by its subpoena both the attendance and testimony of witnesses and the production of books and papers relevant to such investigations.
55 ILCS 5/3-14026