Mich. Comp. Laws § 24.279
An agency, 1 or more members of the agency, a person designated by statute or 1 or more hearing officers designated and authorized by the agency to handle contested cases, shall be presiding officers in contested cases. Hearings shall be conducted in an impartial manner. On the filing in good faith by a party of a timely and sufficient affidavit of personal bias or disqualification of a presiding officer, the agency shall determine the matter as a part of the record in the case, and its determination shall be subject to judicial review at the conclusion of the proceeding. When a presiding officer is disqualified or it is impracticable for him to continue the hearing, another presiding officer may be assigned to continue with the case unless it is shown that substantial prejudice to the party will result therefrom.
MCL 24.279