If any shipment of plants or things which is passing through any portion of the state is, or is liable to be, infested or infected with any pest, and there exists danger of dissemination of the pest while the shipment is in transit in this state, the shipment shall be placed within sealed containers which are composed of metal or other material so constructed that they are not liable to be broken or opened while in transit so as to permit the pest to escape. The containers shall not be opened while within the state.