Several homes at Whakatu north of Hastings were evacuated on Wednesday after an ammonia leak was detected at a factory.
No injuries have been reported Cedenco Foods, where the leak occurred.
About 10 kilograms of ammonia escaped from a discharge tube on the factory roof before the leak was fixed.
The fire service in Hastings says everything quickly returned normal as a steady breeze helped disperse the ammonia gas into the atmosphere.
Police, fire service and ambulance staff attended the scene and some roads in the area were closed.