Fire and Emergency New Zealand received a call at 11.35am after passersby spotted the flames from Wright Rd.
A spokeswoman for Fenz said the fire was not near any buildings and was spreading very slowly.
Two ground crews, one from Millers Flat and another from Roxburgh were in attendance.
Later, a Fenz spokesman said as of 1.30pm, the fire had been contained and largely extinguished.
Ground crews used foam to blanket most of the area.
The helicopter was being used to reach the areas ground crew could not, he said.
A second helicopter was requested, but stood down shortly after arriving.