The fire which closed part of the main road from Welshpool to Guilsfield last night took four fire appliances to be brought under control.
The fire in a steel and timber cladded shed at Pentre Groes, opposite the Red Bank turning, was tackled by up to six firefighters wearing breathing apparatus using four hose reel jets.
Police were on the scene managing the traffic flow after one side of the road was required to be closed.