A corrosive acid spill closed a section of State Highway 2 near Awatoto for more than three hours this afternoon.
Traffic was diverted on the arterial route after corrosive acid was emitted from the chimney stack at Ravensdown fertiliser factory.
Fire communications shift manager Craig Dally said they were notified about the spill at 12.22pm and sent two fire crews to the scene.
Large quantities of a dried product had spilled on the road and firefighters blocked the surrounding drains before they sprayed the substance to dilute it.
A Ravensdown spokesman said the corrosive acid, created through the manufacture of super phosphates, had sprayed onto the nearby train track and road.