Police are investigating arson as the possible cause of Wednesday's fire that threatened four rural homes and burnt 62 hectares of grassland outside Bungendore.
Monaro District police are investigating the cause of the fire, which began near where the Kings Highway crosses Butmaroo Creek about 10kms from Bungendore, about 2.30pm.
The ignition point of the fire, on the banks of the creek and within walking distance of the roadway, was accessible on foot.
When the smoke was first spotted, an observation team in a helicopter was quickly put into the area to assess the fire. They reported it as tracking west through dry grassland toward Bungendore, with a high flamefront.
Fire strike teams were dispatched at 3.07pm.
As the fire intensified, additional resources were called and at one stage there were at least 100 firefighters on the ground, as well as two helicopters attacking the fire with water buckets.
NSW Rural Fires Service spokesman Paul Jones said four homes on rural residential properties were threatened by the fast-advancing fire. At times, thick smoke drifted across Bungendore and caused significant alarm across social media channels.
The Kings Highway was also closed to traffic for several hours.
"There were 10 local fire tankers and four national parks fire crews in there at one stage to help out the property owners," he said.
"The fire came very close to those houses and required a pretty intense effort to save them. It was a close-run thing."
No houses or structures were damaged, but the fire burnt out kilometres of fencing and farm equipment.
RFS volunteers are continuing to patrol the area intermittently to ensure the fire is completely extinguished.
