The blaze - which had been burning since Thursday night - had torn through more than 100 hectares of pine forest north of Waipara.
It had been contained but was not yet under control, Fire and Emergency New Zealand said.
Crews had been monitoring the site overnight on Friday, and heavy machinery and helicopters had been brought in to fight the fire today.
The fire was visible from the road, but neighbouring properties were not in danger.
Fenz said it could take days to extinguish.
Earlier this year, a 300ha vegetation fire in the Waikari Valley forced the evacuation of properties in Waipara.
Meanwhile, firefighters responded to a house fire in Wairarapa in the North Island this morning.
Seven trucks were called to a residential property in the seaside town of Castlepoint about 4.30am.
Fenz said an investigator had been sent to the site, but there were no indications so far the fire was suspicious.
Crews had extinguished the fire and were dampening down the scene.
