70 ILCS 1837/145
The Board may investigate conditions in which it has an interest within the boundaries 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 such 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 has the 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 any investigation or to any hearing before the Board or any member thereof.
Any circuit court of this State, upon application of the Board, or any member thereof, may in its discretion compel the attendance of witnesses, the production of books and papers, and the giving of testimony before the Board or before any member thereof or 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 1837/145