70 ILCS 1807/155
The Board may investigate conditions in which it has an interest within the area of the district; the enforcement of its ordinances, rules, and regulations; and the action, conduct, and efficiency of all officers, agents, and employees of the district. In the conduct of investigations the Board may hold public hearings on its own motion and shall do so on complaint of any municipality within the district. Each member of the Board shall have power to administer oaths and the secretary, by order of the Board, shall issue subpoenas to secure the attendance and testimony of witnesses and the production of books and papers relevant to investigations and to any hearing before the Board or any member of the Board.
Any circuit court of this State, upon application of the Board or any member of the Board, may in its discretion compel the attendance of witnesses, the production of books and papers, and giving of testimony before the Board, before any member of the Board, or before any officers' committee appointed by the Board by attachment for contempt or otherwise in the same manner as the production of evidence may be compelled before the court.
70 ILCS 1807/155