Defence Force training exercises have been linked to a second big fire this week.
A fire at the training ground in Waiouru which started during a live firing exercise on Tuesday has burned about 350 hectares of bush and scrub.
Five civilian helicopters, an Iroquois, a water tanker and fire crews battled the blaze on Thursday.
A Defence Force spokesperson says the fire is contained in a gully in the Three Kings area and there is no risk of it breaching the training area. No one has been injured.
Meanwhile, police and the Defence Force are investigating a fire at West Melton, near Christchurch, on Wednesday.
The Defence Force says it is obvious live grenade training under way at the time is linked to the fire, which tore through 1km of scrub and forced the evacuation of houses.
Detective Inspector Tom Fitzgerald says there is no evidence to indicate that the Defence Force was reckless while carrying out grenade training, as it had a fire crew present during the exercise
and recognised there was a risk.
The commandant of Burnham Military Camp, Major Bill Blair, believes the investigation will look at how the fire started, if normal regulations were in place and will make recommendations to improve processes.
The investigation is expected to take several weeks.