The Secretary may administer oaths and affirmations, take depositions, and require by subpoena the attendance and testimony of witnesses and the production of documentary evidence relating to any matter under investigation or the subject of any hearing. The circuit court of any county may compel obedience to any subpoena. After claiming a privilege against self-incrimination, no individual may be prosecuted or subjected to any penalty or forfeiture for any matter concerning which he may be compelled to testify or produce evidence in obedience to a Department subpoena, except for perjury committed in testifying.