A major fire destroyed part of a large fertiliser factory, sending black smoke billowing across Christchurch this morning.
The fire, at the Ravendsown factory in the busy Christchurch suburb of Hornby, also caused traffic chaos as police cordoned off several roads to create a perimeter around the 14-hectre factory site.
Hairdresser Hanna Kearney noticed black smoke coming from the factory about 10.15am.
She said she had to alert Ravensdown.
"I ran over there and I explained how big and serious this was. They weren't too sure - they were just putting on their fire jackets. I said 'you have to evacuate this place right now - it's been going for about 15 minutes'. They all just started evacuating.
"I went down and had a look in front of the building that was in flames ... then there was quite a big explosion."
Local resident Jamie Rudman could see the flames from the ABC Wigram Pre-School.
He said he quickly raced to Main South Road, where the factory is located.
"Just thick, black smoke pouring off the top of the factory. Got down here as quick as possible 'cause only live around the corner - thought it could've been one of the houses goin' up."
The Fire Service had dowsed most of the blaze by midday.
Canterbury assistant area commander Steve Kennedy spoke with media at the cordon and said the black smoke wasn't toxic.
He said the fire spread because it made its way onto a conveyor belt.
"The conveyor belt runs right down through the length of that building," he said.
"Once we got a fire up in the framing of that building, and the roofing and the exterior cladding, it's going to catch onto that conveyor and spread along through there."
Mr Kennedy said the shed was about 100 metres long, and the fire took out a reasonable chunk of the building.
"It's quite a large building. Like through the roof area, probably about a third of the way through it.
"The crews have done a great job in stopping it spreading into the sulphur store, which was a big risk here for us. The conveyor links into that sulphur store."
Ravensdown chief executive Greg Campbell said the company would assess whether production needs to be shifted off-site.
He said it was lucky the firm had factories in other parts of the country.
"We are fortunate that we do have three manufacturing sites - one in Napier and also one in Dunedin - and they have capacity, so we're fortunate to call on them to assist farmers with their products."
Mr Campbell said the fire was completely out, which meant they were now able to assess the extent of the damage.
He said the company will debrief all 150 staff members tomorrow about the event and what it's planning to do.
The firm had started its own investigation, and the Fire Service is also investigating, although no cause had been determined.