(a) The agency may order a reconsideration of all or part of the case on its own motion or on petition of any party. The power to order a reconsideration shall expire thirty (30) days after the delivery or mailing of a decision to respondent, or on the date set by the agency as the effective date of the decision if such date occurs prior to the expiration of the thirty-day period. If action is not taken on a petition within the time allowed for ordering reconsideration the petition shall be deemed denied.

(b) The case may be reconsidered by the agency on all the pertinent parts of the record and such additional evidence and arguments as may be permitted, or may be assigned to a hearing officer. A reconsideration assigned to a hearing officer shall be subject to the procedure provided in