Fireworks are believed to have started a large scrub fire in the crater of Auckland's Mt Eden.
The fire burned through an area of 200m by 200m inside the dormant volcano.
The flames were fuelled by strong winds which pushed the fire up the sides of the crater.
"It was quite difficult because of the strong winds and it was pushing the fire quite rapidly up the flanks so it was a concern it might head down to where the houses were," City Senior Station officer Sulu Devoe said.
Thirty-six firefighters and nine appliances were involved in tackling the fire, an extra tanker also had to be called in from Papakura.