Residents near the Hampton Downs landfill have been advised to close doors and windows and stay inside as a fire at the dump continues to rage on.
Fire and Emergency New Zealand has asked those who live within 10km downwind of the landfill to avoid breathing in the smoke because the smoke may be toxic due to the range of household waste products burning at the site.
Rural residents within that area who used roof water should stop collecting it immediately and clean their roof before collecting water again, the organisation said.
Three helicopters, four pump trucks and six tankers were helping bring a blaze at the Waikato landfill under control.
Fire and Emergency NZ northern communications shift manager Scott Osmond said the fire was about 30m by 40m, based at the head of the tip at Hampton Downs.
Although the crews were still trying to bring it under control there were no concerns that it would spread to any neighbouring properties.
Area commander Daryl Trim said the fire was contained but it may take several days to extinguish completely.
The landfill, the region's largest, is built on 386ha and sits north of Te Kauwhata.