Any party who desires a continuance, shall immediately upon receipt of notice of a hearing, or as soon thereafter as facts requiring such continuance come to his knowledge, notify the agency of said desire, stating in detail the reasons why such continuance is necessary. The agency, in passing upon a request for continuance, shall consider whether such request was promptly and timely made. For good cause shown, the agency may grant such a continuance and may at any time order a continuance upon its motion. During a hearing, if it appears in the public interest or in the interest of justice that further testimony or argument should be received, the agency may in its discretion continue the hearing and fix the date for introduction or additional evidence or presentation of argument. Such oral notice shall constitute final notice of such continued hearing.