A major fire erupted in an east-end Montreal recycling plant where part of the roof collapsed Wednesday afternoon.

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Firefighters battle a large blaze in a recycling plant in the east-end of Montreal on Wednesday. ((Ryan Remiorz/Canadian Press))

Between 15 and 20 employees were inside the Recyclage Notre-Dame facility when part of the roof caved in, triggering an electrical fire that spewed thick clouds of dark smoke. Everyone escaped unharmed, Montreal's fire department said.

Flames quickly spread through the building and to the roof, forcing the more than 100 firefighters on the scene to retreat at the height of the emergency, said operations chief Aimé Charette. Natural gas used to fuel the factory's heating system fed the fire.

"The steel structure is already precarious as it is, and we wanted to make sure our guys weren't too close and at risk of being caught in any collapse," Charette told CBC News.

Charette said it's not clear whether snow contributed to the warehouse collapse, but according to a spokesman with EBI Environment, the business that owns Recyclage Notre-Dame, the company was in the process of clearing the roof this past week.

The fire burned mostly cardboard and paper, but provincial environment inspectors were called to the scene to assess the smoke's toxicity, which they said was low.

Employees tried to extinguish fire

Employee Vincent Delouis said workers tried to put out the fire with extinguishers but were unable to get it under control and had to flee. One part of the roof that caved in landed directly on a large stack of papers, he said.

The recycling plant, which processes mostly household waste, is at the corner of Lakefield and Notre-Dame streets in Montreal's east-end refinery district.

Record-breaking snowfalls in parts of Quebec this winter have caused several building cave-ins that have killed four people in the last week.

The province's largest school board cancelled classes for two days to clear snow from its building roofs.

More snow and rain fell Wednesday in Montreal, with precipitation forecast in the coming days.

With files from the Canadian Press