All interruptions of regular service that are likely to continue for more than twenty-four hours shall be promptly reported in writing to the Department with a full statement of cause of such interruption and its probable duration; however, any interruption of regular service that results from an act of God need not be reported to the Department unless it continues for more than seventy-two hours. All interruptions of regular service shall be promptly reported to the agents of the carrier on the routes involved.