By general or special rule the board creating a planning agency may provide that other matters shall be referred to the planning agency before final action is taken thereupon by the board or officer having final authority on the matter, and final action thereon shall not be taken upon the matter so referred until the planning agency has submitted its report within such period of time as the board shall designate. In reporting upon the matters referred to in this section the planning agency may make such investigations, maps, reports and recommendations as it deems desirable.