Fire and Emergency are scaling back operations at a blaze at a Waikato landfill for the night.
The fire at the Hampton Downs Landfill is contained, and one truck remains at the scene.
Residents are still being warned to stay inside and shut their doors as a precautionary measure.
More crews will be onsite tomorrow to continue fighting the blaze near Meremere and the Spring Hill prison.
Fire and Emergency shift manager Scott Osmond said the smoke may be toxic and residents who lived within 10 kilometres downwind of the fire should avoid breathing in any smoke.
"There has been chemicals dumped in that landfill over the years and there is a remote possibility that there will be chemical residue getting into the air so the advice is that for anyone immediately downwind or getting any smoke in their area, they should just stay inside with doors and windows closed."
Scott Osmond said the fire may take several days to extinguish.
Any rural residents who collect roof water should stop using it immediately.
Waikato Regional Council said there had not been any run-off into nearby waterways from the firefighting efforts.