The department may subpoena witnesses, administer oaths, and require the production of records, books, and documents for examination at any hearing or investigation conducted by it. No person shall be excused from attending and testifying, or from producing books, papers, and records before the department or a court, or from obedience to the subpoena of the department or a court, on the ground or for the reason that the testimony or evidence, documentary or otherwise, required of the person may tend to incriminate the person or subject the person to a penalty or forfeiture: PROVIDED, That nothing herein contained shall be construed as requiring any person to produce any books, papers, or records, or to testify in response to any inquiry not pertinent to some question lawfully before the department or court for determination. No person shall be subjected to criminal prosecution or to any penalty or forfeiture for or on account of any transaction, matter, or thing concerning which, in spite of his or her objection, he or she may be required to testify or produce evidence, documentary or otherwise before the department or court, or in obedience to its subpoena: PROVIDED, HOWEVER, That no person testifying shall be exempt from prosecution and punishment for perjury committed in so testifying.