Homes were evacuated as about 60 fire fighters battled a sulphur blaze at a Hawke's Bay fertiliser plant which had the potential to turn "particularly nasty". The fire broke out in a five-storey-high sulphur shed at the Ravensdown plant between State Highway 2 and Waitangi Rd at Awatoto, south of Napier, at about 2.45pm on Thursday. Crews from across the region were called in to fight the blaze in the shed containing about 800 tonnes of sulphur. Properties in the area were evacuated as potentially dangerous sulphur dust - which can combust at relatively low temperatures - and other hazardous material was blowing from the plant. Roads in the area were closed, including State Highway 2 between Napier and Hastings, which runs past the plant. Anyone travelling between the two cities was advised to use the Napier-Hastings expressway rather than the SH2 route. Sergeant Greg Simmons said people along along McLeod Rd, west of the plant, were being evacuated as a precaution. There were concerns any chemicals burning may cause toxic smoke to be ingested. "We are evacuating residents along McLeod Rd and we have looked at [nearby] Awatoto Rd and Waitangi Rd," he said. Cyclists biking along the waterfront were also being asked to avoid the area. Fire service assistant area commander Nigel Hall said 60 fire fighters were at the scene and he expected it would be a "long drawn out" incident. "We have got a smouldering fire in the second shed. In there we have got about 800 tones of Sulfur which is particularly nasty," he said. "We have been inside the building fire fighting working with low pressure deliveries. There is a possibility of dust explosions with this particular product so the people working inside are only using spray instead of jets." Hall was unsure how the fire started but believed it began on the conveyer belt which runs across the top of the sulphur shed.