The walls of a Beltline building gutted by fire are being knocked down Monday because the structure is unsafe, said Calgary officials.

Traffic was rerouted around the area as crews fought the building fire.
(Tremaine Lea)

The fire department warned drivers to avoid the area around 14th Street and 17th Avenue S.W. Monday as a trackhoe, or heavy equipment excavator, tears down the building that used to house a bike shop and a boutique.

Fire investigators and the arson unit will resume their probe into the cause of the blaze when it's deemed safe to enter the area.

Thick smoke billowed over several blocks in the southwest neighbourhood as crews responded to the fire on Sunday evening. Firefighters had to force their way through security doors and windows of the building to get inside, said fire officials.

More than 30 firefighters responded to the blaze in southwest Calgary Sunday.
(Andree Lau/CBC)

No one was hurt in the blaze, but two stores — the Westside Mountain Shop and Phyne Fashions — suffered significant damage. Several blocks around the fire were blocked off to traffic for several hours.

Customers and staff were evacuated from an adjacent pub and a McDonalds restaurant, but the businesses were not damaged.

More than 30 firefighters responded to the blaze, which was brought under control after about two hours.

Police guarded the scene overnight to make sure no one entered the building.