Six helicopters and ground crews are battling to control a fire covering 800ha on Mount Prospect, near Te Anau.
Fire and Emergency New Zealand shift mangaer Andrew Norris said a call was received around 2pm today after a burn-off at Mt Prospect Station got out of control.
"It's currently burning 800ha, it's a huge fire," he said.
Mr Norris said the fire was moving up the side of Mt Prospect.
"We've got about six aircraft working on the fire to protect the repeater at the top."
"There's no buildings, no homes or anything threatened, but there's a big repeater — that's the only thing," Mr Norris said.
Area resources were working hard to control the blaze, but were struggling with wind and weather conditions, he said. It was hoped the conditions would better in the coming hours.
Mr Norris said it was the biggest fire that he was aware of to have occurred in the area.
Smoke was reported to be seen and smelled as far away as Wreys Bush.