Sixty staff face an uncertain future after a large fire destroyed part of a Christchurch gelatine factory.

A major fire erupted at the Gelita factory in Connal St, Woolston, about 11.25pm on Thursday. It was brought under control by 7am on Friday.

Gelita general manager Gary Monk said the factory's 60 staff had been called to a meeting on Monday.

SUPPLIED Fire crews battled a massive blaze at the Gelita factory in Christchurch overnight.

He said it was too early to forecast the long-term impact the fire would have on staff and production, but the company was insured.

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"It's not only the buildings, it's all the electrical infrastructure in there as well, you know. All that stuff takes time to set up.

JOHN KIRK-ANDERSON/STUFF Gelita general manager Gary Monk said 60 staff had been called to a meeting on Monday.

"It's not going to be weeks, it's going to be months."

Insurance assessors had been on site on Friday and a decision would eventually be made about whether or not the company rebuilt on the same site.

"There's not enough information to make any decision like that.

JOHN KIRK-ANDERSON/STUFF The future of Christchurch gelatine factory is unclear after it went up in flames overnight Thursday.

"There's always ins and outs with insurance but we're definitely covered for fire insurance so it's just a matter of working out where that takes us."

Monk said it was unclear when staff could return.

"These guys [fire investigators] need some time to look through the site, they don't want anyone touching anything so we'll just shut up shop and we'll have to shut down some of our logistics chains."

He said the fire came at a time Gelita was "clawing our way out" of a tough seven years, with new projects on the agenda and staff working on equipment upgrades.

"It's a bloody terrible call to get. The staff will be gutted because they've worked so hard to get it back up.

"[But] we've had a hammering through the earthquakes and that, so we've got a reasonable level of resilience."

JOHN KIRK-ANDERSON/STUFF Damage to the factory building is visible on Friday morning.

New Zealand Meat Workers and Related Trades Union president John Reid said 30 of the 60 workers at the factory were represented by the union.

"It sounds like this is pretty monumental," he said.

"The company has interruption insurance that will look after wages in the interim. Everybody's wellbeing will be paramount with that company. When they had the earthquakes they were brilliant with their staff."

JOHN KIRK-ANDERSON/STUFF The fire was "well-involved" when crews arrived just before midnight.

Reid said he did not know how long the interruption insurance would cover wages or if the company would rebuild on that site.

"They have ridden some hard times with the earthquake and then, once they get over that, this comes along. Who knows what will happen there."

In 2014, Gelita announced it was investing $24 million to upgrade its Woolston site. About 70 to 80 per cent of the company's product went offshore.

JOHN KIRK-ANDERSON/STUFF Three fire crews remained on site at the factory on Friday morning dampening down hot spots.

Monk had "no idea at this stage" what caused the fire that tore through up to 10,000 square metres of the factory, which had operated at the site for more than a century.

Four staff members were on site at the time the fire was reported and all managed to evacuate without injury.

WHITE LIGHTNING 'LIT THE SKY'

JOHN KIRK-ANDERSON/STUFF The fire triggered explosions and sent white lightning shooting skyward, station officer Brian Lewis says.

Fire safety officer Brian Lewis was among the first on the scene.

He said the smoke pouring from the factory was "straight up and huge".

"We were only 200 metres from the station . . . it was an overcast night and we could see the smoke just going straight up."

Lewis said the cloud was likely caused by the fibreglass roof of the building catching fire.

"There were plenty of explosions . . . and there was white lightning that just lit the whole sky."

It was too soon to say what could have caused the explosions.

The products produced on site were not highly flammable, but some chemicals were also stored in the building that caught fire, Lewis said.

Environment Canterbury (ECan) had also been called, a Fire and Emergency NZ spokesman said.

"They were worried about water run-off running into the Heathcote River . . . but they blocked the drains."

SMELL COMPLAINTS

The Gelita factory has been the subject of hundreds of smell complaints and has received multiple ECan fines for breaching consents relating to odour.

Controversy relating to the smells escalated following the development of popular boutique mall The Tannery nearby.

In 2015, the German-owned factory was given a change to its permit allowing it to release offensive odours for two years while it underwent a multi-million dollar upgrade to fix the smell.

However, in 2017 another 131 complaints about odours were lodged and eight were substantiated.

Alasdair Cassels, owner of The Tannery, said losing the factory that had been part of the area for a century was "a sad day for Woolston".

Aside from a few "particularly smelly" days in recent times, Cassels said the company "had gone a long way to getting rid of their problem".

"That history and that factory's been there for a long time.

"I was never one to say 'go away', I was always saying 'just live within the consent', and I think they were trying to do that so generally this is a sad day."