"There is still a threat to the overhead transmission lines. The fire is still active but at this stage it is being well managed," he said.
Last night the fire was 100m from the main powerlines that run to the smelter, and 400m from the smelter itself.
Dunn said crews would be rotated in coming hours just before the blaze hit the 12-hour mark.
Dunn said the fire was difficult to reach as there were no roads into the area. Four helicopters with monsoon buckets were first to tackle the blaze.
"Its been a long fire. We've been trying to protect the Tiwai smelter, which they're doing a great job of and firefighter operations will just continue," he said.