If, after wagering has begun on a race, a horse, programmed to start as part of a coupled entry or field is scratched in such race, all betting upon such coupled entry or field shall cease and all money theretofore wagered upon such coupled entry or field shall be refunded. Notwithstanding the termination of betting upon all horses that are part of such coupled entry or field, the horse or horses in such coupled entry or field that are not scratched shall start in such race as nonbetting interests for the purse and the finish of such horses in the race shall be disregarded for pari-mutuel purposes. Such circumstances shall be announced by public address and explained to the public at the time of such action and thereafter as may be necessary to adequately inform the public.