The Defence Force says a stray piece of shrapnel in a planned firing exercise was to blame for a fire which started at West Melton near Christchurch on Wednesday.
Residents want police to investigate why a rifle range was used for grenade practice on a hot dry day, igniting fires that engulfed about 50 hectares.
Brigadier Peter Kelly said it is important for the New Zealand Army and other forces to be able to have hot, dry conditions to train in, but the Defence Force is deeply sorry for the destruction caused and thought it had the correct measures in place to prevent a fire.
Brigadier Kelly said training is suspended until weather conditions improve.
Police say there is nothing to suggest recklessness, but the fire is being investigated.
Meanwhile, a fire near Waiouru which burned 350 hectares of bush and scrub over two days was by Thursday night contained to a five-hectare gully.
The Defence Force said it started on Tuesday during a live firing exercise by soldiers from Singapore in an isolated part of the Waiouru training grounds.