A huge wildfire continues to burn through Tongariro National Park - with the cause still not known

The blaze has caused evacuations of dozens of hikers and residents , and has now burned through up to two and a half thousand hectares.

Fifteen Fire and Emergency helicopters and five fixed wing planes are grounded due to cloud cover, but are on standby to continue battling the blaze when it clears.

Emergency Management Minister Mark Mitchell says there's still been no indication of how the fire started.

He says Fire and Emergency have an idea where it started, and will be investigating.