(a) Investigational hearings, as distinguished from hearings in adjudicatory proceedings, may be conducted in the course of any investigation undertaken by the Commission, including inquiries initiated for the purpose of determining whether or not a person is complying with an order of the Commission.

(b) Investigational hearings may be held before the Commission, one or more of its members, or a duly designated representative, for the purpose of hearing the testimony of witnesses and receiving documents and other data relating to any subject under investigation. Such hearings shall be stenographically reported and a transcript thereof shall be made a part of the record of investigation. [Rule 285.]