Around 120 firefighters and support crew have been involved in ground operations to battle the fires that broke out on Monday night.
He said the plan was to let it burn itself out, and that a forecast of rain over the weekend would help.
Drizzle was falling in Christchurch on Friday morning, with hopes it would dampen fires in the Port Hills.
The emergency has so far claimed one life, when a helicopter that was dumping water on the flames crashed Tuesday and killed pilot Steve Askin, a decorated special forces veteran.
A state of emergency has been declared in the area and authorities have been sent in to help firefighters with the two fires.
"It is frightening to watch the glow of the fire on the hills at night and to see these fearless people in helicopters disappear into the huge plumes of smoke to subdue the flames".
Helicopters have been battling the blaze for days. His formerly secret role in defense missions in Afghanistan were only revealed after his death. Local media attributed the first fire to an electrical fault. "While there are still areas burning out of control, the fire is contained within the 2,075 hectare area", Christchurch Civil Defence official Dave Adamson said in a statement.
Fires of this intensity are rare for New Zealand.
He agreed that was true, but said doing so required full knowledge of the scene, and there are structures in place for those with that information to make the decision that need to be fixed in future. Selwyn Mayor Sam Broughton said changing winds had made the fire unpredictable.
Wildfires of such ferocity are rare in New Zealand, where regular rainfall usually prevents them reaching the intensity seen in places like Australia and the U.S. west coast.