A massive fire that destroyed an industrial building and damaged two others on Annacis Island is finally out, more than 20 hours after it started.

Firefighters had to work through the night to contain a stubborn blaze that broke out at a building owned by Ideal Welders Monday afternoon, triggering a large emergency response on the small Fraser River island.

On Tuesday morning, 43 firefighters with 10 firetrucks were still battling what officials are calling the largest structure fire in the Delta Fire Department’s history.

"Other than a bog fire, this was one of our bigger fires -- probably the biggest fire for a commercial building we've ever had," Delta Fire Chief Dan Copeland told CTV News.

Workers started showing up at the property Tuesday anxious to find out whether they would be out of work.

Chris Mitchell, who only recently got a job with the company, told CTV News about 50 or 60 people are employed at the site.

"I don't think anyone was working over the weekend, so everyone's safe and out of there. That's good," Mitchell said.

Mitchell and other employees, however, are confident they won’t be out of work for long.

“The union hall always takes care of their guys,” he said.

The fire spread quickly and damaged other buildings on Annacis Island belonging to the same company. Copeland said renovations and additions to the property complicated firefighters' efforts.

"They were offensive for the first part of the fire and thought they were getting the upper hand, but there's a lot of void spaces, a lot of different add-ons to the building. A very tough, stubborn fire to fight," Copeland said.

At one point, crews were also forced to retreat from the warehouse over concerns about potentially toxic chemicals inside. A thick chemical smell remained in the air Tuesday morning.

"There's a lot of concern around compressed gasses and those types of things, so we want to make sure our firefighters are safe and maintain a distance," Copeland said.

Even by around noon, some hot spots were still flaring up in the charred warehouse. Crews said they might have to bring in excavators to knock down walls to completely extinguish the smouldering blaze.

The cause of has not yet been determined.

Investigators are now in the painstaking process of piecing together a timeline and map of how the fire started and spread.

CTV News has learned roofing work was being done on the building before the fire started, but investigators were only able to start looking at potential sources late Tuesday morning and have not come to any conclusions.

With a report from CTV Vancouver's Ben Miljure and Penny Daflos