Me. Rev. Stat. tit. 7, § 456

The commissioner or the commissioner's duly authorized agent may investigate, upon the complaint of any interested person, or on the commissioner's or the agent's own motion, the conduct and activities of any person applying for or holding a license under this subchapter and, for that purpose, may examine the books and papers of any applicant or licensee and may require testimony and affidavits thereon under oath. The commissioner may, in a manner consistent with the Maine Administrative Procedure Act, conduct such hearings as the commissioner considers necessary pursuant to this subchapter. The commissioner has full power to subpoena such witnesses and documents as the commissioner considers necessary.