225 ILCS 2/155
The Department shall have power to subpoena and bring before it any person in this State and to take testimony either orally or by deposition or both with the same fees and mileage and in the same manner as prescribed by law in judicial proceedings in civil cases in circuit courts of this State. The Department shall also have the power to subpoena the production of documents, papers, files, books, and records in connection with a hearing or investigation.
The Secretary and the hearing officer designated by the Secretary shall each have power to administer oaths to witnesses at any hearing that the Department is authorized to conduct under this Act and any other oaths required or authorized to be administered by the Department under this Act.
225 ILCS 2/155