Firefighters in Coquitlam, B.C., were busy battling a large fire at an industrial building near Schoolhouse Street early Thursday.

The blaze started just after midnight at a masonry building and had already made its way through most of the interior by the time crews arrived.

The fire sent a cloud of thick black smoke high into the air for several hours as crews were forced to fight it from the outside. Metro Vancouver said it would be monitoring air quality in the region Thursday morning as a result.

Assistant Chief Gary Mulligan with Coquitlam Fire said exposure to active power lines and the structural integrity of the building were just two of the hazards his crews were up against.

<a href="https://twitter.com/hashtag/BREAKING?src=hash&ref_src=twsrc%5Etfw">#BREAKING</a>: large industrial fire in <a href="https://twitter.com/hashtag/Coquitlam?src=hash&ref_src=twsrc%5Etfw">#Coquitlam</a> near Schoolhouse <a href="https://t.co/CG2PVkVdak">pic.twitter.com/CG2PVkVdak</a> —@gpsmendoza

"Whatever was burning … was undetected for some time," said Mulligan.

"It got a good hold in the roof structure … it's very unsafe to put firefighters on the roof after a certain point and it becomes a safety issue all the way around."

The cause of the fire is still under investigation.

Getting reports that the smoke from this <a href="https://twitter.com/hashtag/Coquitlam?src=hash&ref_src=twsrc%5Etfw">#Coquitlam</a> fire is being smelled all the way in <a href="https://twitter.com/hashtag/Vancouver?src=hash&ref_src=twsrc%5Etfw">#Vancouver</a> due to the wind direction. <a href="https://t.co/vwL2Ayvrnn">pic.twitter.com/vwL2Ayvrnn</a> —@gpsmendoza

With files from Gian-Paolo Mendoza