(a) Any employee of an enforcement agency who investigates, or receives information of, an accident involving a snowmobile shall make a written report of the investigation or information received, and such additional facts relating to the accident as may come to his knowledge, and mail the same within 48 hours to the bureau, keeping a record of same in his office.

(b) Where a serious injury or death has resulted from such accident, the investigating officer may delay mailing his report to the bureau pending a final determination as to the condition of the injured person or persons; however, in such cases the investigating officer or his superior must promptly notify the bureau by telephone, teletype or in writing of such delay and the reason therefor. Said written report is to be filed not later than seven days after the accident.