One person is suffering from chemical burns after a "significant" ammonia leak at a Taranaki meat processing plant.

Cordons stretching to around 1km are surrounding the site of the spill at Silver Fern Farms on Tawhiti Rd.

Fire and Emergency services central manager Belinda Beets said up to 20,000 litres of ammonia was at risk of leaking, but most of that was contained.

It was unclear how much had leaked at the plant, but Beets said it was a significant leak.

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"We are warning people who are living within a 1km radius to make sure door and windows are closed," Beets said.

Residents were also warned not to use air conditioning.

Beets said nine fire appliances were at the plant, with the leak reported just after 4pm.

Silver Fern Farms spokesman Justin Courtney said staff should have the spill controlled and the plant operational by tomorrow.

He expected staff would return to work at the plant this evening.

Police were also at the scene and thanked the public for their assistance.