Firefighters are attempting to rein in a massive fire near Meremere in Waikato, burning through 477 hectares of swamplands across a 10-kilometre perimeter

It's spreading through the Whangamarino wetlands, a Department of Conservation area of environmental significance.

Eight helicopters, two planes and 40 personnel are battling the blaze, that broke out yesterday.

Incident Commander Mark Tinworth says no properties are threatened, but some businesses could have to remove dangerous material if the fire gets too close.

He says bringing it under control could take at least another day.