Loud bangs that Lyttelton residents thought were fireworks rang out before a blaze engulfed the hold of a tuna trawler last night.
Up to 60 firefighters and 16 appliances battled for 12 hours overnight to extinguish the fire on board the 60 metre fishing ship, Ocean Breeze.
They all donned breathing apparatus after discovering the trawler was leaking ammonia.
The toxic gas is still leaking from the vessel this morning and three fire crews and a command unit are still at the Stark Bros Ltd dry dock at Godley Quay.
Firefighters in oxygen masks are using a gas axe to cut a hole in the front hull of the ship.