The Lowari Tunnel, a 10.4km tunnel under the Lowari Pass that connects Dir and Chitral, is snowed in.
Two feet of snow has accumulated in the tunnel and the administrations says work to clear it is under way.
But so far, an 8.5km section to the tunnel has become very difficult for motorists to cross.
Many cars are stuck in the snow. Some drivers have attached chains to their tyres and parked on the side.