When the Attorney General requires the attendance of any person, as provided in Section 9, he shall issue an order setting forth the time when and the place where attendance is required and shall cause the same to be served upon the person in the manner provided for service of process in civil cases at least 14 days before the date fixed for attendance. Such order shall have the same force and effect as a subpoena and, upon application of the Attorney General, obedience to the order may be enforced by the circuit court in the county where the person receiving it resides or is found, in the same manner as though the notice were a subpoena. Such court may, in case of contumacy or refusal to obey the order issued by the Attorney General, issue an order requiring such person to appear before the Attorney General or to produce documentary evidence, if so ordered, or to give evidence touching the matter in question, and any failure to obey such order of the court may be punished by that court as a contempt upon itself. The investigation or hearing may be made by or before any Assistant Attorney General designated in writing by the Attorney General to conduct such investigation or hearing on his behalf. Witnesses ordered to appear shall be paid the same fees and mileage as are paid witnesses in the circuit 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 the circuit courts of this State. The Attorney General or the Assistant Attorney General acting in his behalf is empowered to administer the necessary oath or affirmation to such witnesses.