One person has been injured following an ammonia leak at a Canterbury processing plant.
Fire and Emergency NZ was called to the Synlait site, which was evacuated, at Dunsandel, north of Ashburton, about 10am today.
The leak has since been isolated.
Fire and Emergency relieving shift manager John Ditmer says two people were treated by medical staff following the leak.
He confirmed fire crews left the scene at 12.30pm and cordons had been removed.
A damage valve during routine maintenance is believed to have activated the ammonia detection system, triggering the plant evacuation.
A Synlait spokesperson confirmed one employee was taken to hospital as a precaution.
Six fire crews from Dunsandel, Rakaia, Burnham, Leeston and Wigram were at the scene.