Firefighters were called to Mole Hill Road, by Fuschia Creek, yesterday at 3.10pm.
Fire and Emergency New Zealand shift manager Jill Higgison said a farmer had been carrying out a controlled burn off when it got out of hand.
Two rural ground crews and five helicopters were working to contain the blaze that had today spread across roughly 800 hectares.
She said as of 10am, two ground crews were "being lifted into the southern flank to carry out mop up".
"It is is slowly spreading, it is not going near any buildings at the moment, they are just trying to contain it."