Fire and Emergency New Zealand assistant area commander Mike Harrison said the fire started as a controlled burn of an area of gorse and scrub on a farm on State Highway 83.
"Unfortunately, in the afternoon the breeze came up," Mr Harrison said.
"[The farmer] had really good fire breaks in place, but embers from the burn crossed the fire break, and set vegetation on fire on the other side."
Crews from Oamaru, Weston, Glenavy, Waitaki and Kakanui were called to the fire when the farmer reported it to emergency services about 2pm.
"He was on site all day watching the fire, and he called us immediately as soon as he saw there were embers crossing over the fire line and that there was a small fire on the other side. He did exactly the right thing, in terms of calling 111 and asking for assistance."
Four helicopters were also called in to assist, due to the steep terrain.
"It was quite difficult to fight, based on the terrain and the vegetation that was burning."
Fire crews left the scene about 10pm on Sunday, and returned yesterday morning to deal to any remaining hot spots.
The area is now in a restricted fire season.
The change for Otago’s Coastal (Dunedin and Waitaki) and Clutha zones came into effect at 8am yesterday, and means permits are now required to light a fire in open air.
Fenz Otago district manager Phil Marsh said there was a lot of long vegetation in the Coastal and Clutha zones that was quickly drying out and could be fuel for a fire.
"This means a fire could spread very easily and get out of control."
In a restricted fire season there are some activities that do not need a permit, such as cultural cooking and barbecues. But anyone lighting a fire would still need to take great care due to the overall fire danger, Mr Marsh said.
"Check the local weather conditions at www.checkitsalright.nz. If it’s hot, windy or the fire danger is high, please don’t light your fire, even if you have a permit."
The Lakes zone and Central zone of the Otago fire district remain in a prohibited fire season. No outdoor fires are permitted in these areas.
