(a) The commissioner shall also have power:
(1) To gather and compile information concerning and to investigate from time to time the organization, business, conduct, practices and management of any person, firm or corporation engaged in intrastate commerce and the relation thereof to other persons, firms and corporations;
(2) To require, by general or special order, persons, firms and corporations engaged in intrastate commerce or any class of them or any of them to file with the commissioner in such form as he may prescribe annual or special or both annual and special reports or answers in writing to specific questions, furnishing to the commissioner such information as he may require as to the organization, business, conduct, practices, management and relation to other persons, firms and corporations of the person, firm or corporation filing such reports or answers. Such reports and answers shall be made under oath or otherwise as the commissioner may prescribe and shall be filed with the commissioner within such reasonable period of time as he may prescribe, unless additional time is granted in any case by the commissioner, and all such reports, answers or information shall be kept confidential by the commissioner, except that such may be used without claim of privilege in any judicial proceeding brought for the violation of any provision of this chapter or in which compliance with this chapter is sought to be enforced and in which the person, firm or corporation so furnishing such report, answers or information is involved as a party or as owner of any article or product involved in such judicial proceeding.
(b) For the purposes of this chapter, the commissioner shall at all reasonable times have access to for the purpose of examination and the right to copy any documentary evidence of any person, firm or corporation being investigated or proceeded against and may require by subpoena the attendance and testimony of witnesses and the production of all documentary evidence of any person, firm or corporation relating to any matter under investigation. The commissioner may sign subpoenas and may administer oaths and affirmations, examine witnesses and receive evidence. Such attendance of witnesses and the production of such documentary evidence may be required at any designated place of hearing. In case of disobedience to a subpoena the commissioner may invoke the aid of any court designated in Section 2-17-30 in requiring the attendance and testimony of witnesses and the production of documentary evidence. Any of the courts designated in Section 2-17-30 within the jurisdiction of which inquiry is carried on may, in case of refusal to obey a subpoena issued to any person, firm or corporation, issue an order requiring such person, firm or corporation to appear before the commissioner or to produce documentary evidence if so ordered or to give evidence touching the matter in question, and any failure to obey such order or any such court shall be punished by such court as contempt thereof.
(c) Upon application of the Attorney General of this state at the request of the commissioner, the circuit courts of the several counties of this state shall have jurisdiction to issue writs of mandamus commanding any person, firm or corporation to comply with the provisions of this chapter or any order of the commissioner made in pursuance of this chapter.
(d) The commissioner may order testimony to be taken by deposition in any proceeding or investigation pending under this chapter at any stage of such proceeding or investigation. Such depositions may be taken before any person designated by the commissioner and having power to administer oaths. Such testimony shall be reduced to writing by the person taking the deposition or under his direction and shall then be subscribed by the deponent. Any person may be compelled to appear and depose and to produce documentary evidence in the same manner as witnesses may be compelled to appear and testify and produce documentary evidence before the commissioner as provided in this section.
(e) Witnesses summoned before the commissioner shall be paid the same fees and mileage that are paid witnesses in the courts of this state, and witnesses whose depositions are taken and the persons taking the same shall severally be entitled to the same fees as are paid for like services in such courts.
(f) No person, firm or corporation shall be excused from attending and testifying or from producing books, papers, schedules of charges, contracts, agreements or other documentary evidence before the commissioner or in obedience to the subpoena of the commissioner whether such subpoena be signed or issued by him or his delegate or in any cause or proceeding, criminal or otherwise, based upon or growing out of any alleged violation of this chapter or of any amendments thereto on the ground or for the reason that the testimony or evidence, documentary or otherwise, required of him or it may tend to incriminate him or it or subject him or it to a penalty for forfeiture, but no person shall be prosecuted or subjected to any penalty for forfeiture for or on account of any transaction, matter or thing concerning which he is compelled, after having claimed his privilege against self-incrimination, to testify or produce evidence, documentary or otherwise; except, that any person so testifying shall not be exempt from prosecution and punishment for perjury committed in so testifying.