A planned burnoff which spread to more than 1300 hectares of land near Te Anau was started in 'appalling' conditions, Fire and Emergency says.
Six helicopters and four ground crews have been fighting the fire today, which started on the side of Mount Prospect just after 2pm yesterday.
The fire has burned through around 1315 hectares of scrub land, native forest and commercial forestry, but it is now under control.
Principal rural fire officer Elton Smith said the fire was the result of an uncontrolled burnoff, which should never have happened in yesterday's warm, dry conditions.
"We've got firefighters and aircraft personnel that are tied up with this incident over a long weekend, when in reality they shouldn't be.
"This fire never should've been lit to begin with in the conditions that were forecast for yesterday.
Winds in the area were gusting 80km/h yesterday but Mr Smith said conditions for fighting the fire were much better today, with little wind and blue sky.
He said yesterday the fire had threatened a communications tower on Mount Prospect, which provides critical infrastructure for the area.
Fire crews would be speaking to the parties responsible for the fire before deciding what action to take.
Mr Smith said there would not be a watch overnight but a fire crew would be checking the area tomorrow morning.