Cordens are in place around a chemical spill in Hawera, in the Taranaki region.
Police were called to the spill at Silver Fern Farms on Tawhiti Rd at around 4:20pm.
People near the spill are asked to close their windows, stay indoors and avoid using air conditioning.
There is a cordon of 1 kilometre around the site of the spill and Fire and Emergency are also at the scene.
Silver Fern Farms has confirmed it has an ammonia leak, and it hopes to have everything back running tonight so work can continue tomorrow.
It is currently working with emergency services to contain the leak.
The manager of GAS in Hawera says there are five fire appliances at the scene and the workers there haven't gone home.
Although his petrol station is 1 kilometre away from Silver Fern Farms, they haven't been able to evacuate.