Official notice may be taken of all facts of which judicial notice may be taken and of other facts within the specialized knowledge of the agency. The noticed fact and its source shall be stated and made known to affected parties at the earliest practicable time, and any party shall on timely request be afforded an opportunity to dispute the noticed fact through submission of evidence and argument. (1973, c. 1331, s. 1; 1985, c. 746, s. 1.)