Fire department spokeswoman Carol Henke says people noticed flames and smoke coming from the top floor of the four-storey project just before noon Saturday.
Henke says that because the building was still under construction, there were a lot of open areas that allowed oxygen to feed the flames.
The site is located just south of Calgary's downtown core, not far from the Saddledome.
The nearby Talisman Centre recreation complex was briefly evacuated due to the smoke, and streets around the fire were blocked off.
Henke says there were workers at the site when the fire started, but there were no reports of injuries.
"It grew very quickly and the plume of dark smoke could be seen across the city," Henke said.
The fire continued to burn through the afternoon and Henke said some of the building had collapsed. She said heavy equipment would be needed to further fight the fire.
There were fears the flames could spread to nearby buildings, but Henke said that didn't happen. A condominium building next door was evacuated and may have suffered some heat damage, she said.
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