The fire blazed across 40ha of native tussock and grassland on Sunday afternoon and threatened to enter the Pisa Conservation Area, before rural firefighters brought the flames under control.
Department of Conservation rural firefighter Paul Hondelink said a fire investigator had been unable to pinpoint the cause of the fire.
The fire appears to have started just beneath a steep bluff, next to the side of the Crown Range Rd, about 10km south of Cardrona and a little short of the township side of the Eastburn Stream bridge.
Three helicopters - two equipped with monsoon buckets, a water tanker and fire crew from Luggate, plus Arrowtown-based firefighters, battled the flames for about six hours before the fire was brought under control.
Mr Hondelink said the area where the fire had started was not a location where a car could have "easily" pulled over to the side of the road.
Queenstown Lakes rural fire chief Gordon Bailey said any information from motorists travelling the Crown Range from midday on Sunday would be welcomed.
"Someone driving over the pass must have seen the fire get away, or where it originated," he said.
Several travelling motorists called 111 at about midday to notify emergency services of the fire.
By the time rural crew members arrived the fire was well established above the road and continued to burn high up the steep mountainsides of the Pisa Range.
The fire came within a kilometre of burning into the Pisa Conservation Area, Mr Hondelink said.
It was too early to calculate how much the fire had cost to extinguish, Mr Bailey said.
An application to the National Rural Fire Fund would be made in due course to cover costs associated with fighting the fire, he said.
Costs can be passed on to any individuals, or persons found responsible for causing rural fires.
