Dozens of Ottawa firefighters descended on a high-rise apartment building on Alta Vista Drive Monday afternoon after a fire started in the basement.

The fire was sparked in the electrical room, and was bad enough that residents who lived as high up as the 16th floor of the 20-storey building could smell the smoke.

The building's alarm went off shortly after 12:30 p.m. Firefighters who responded to the call were worried the electrical transformer could explode, so power was cut to the building.

As a result, two people were stranded in elevators for more than an hour. One of them, a woman, had to be treated for stress and heat exhaustion. 

Monica Farquason, who lives on the 16th floor, said she first noticed something was amiss when the lights went out.

"The light went off, so I was there and hoping that it would come back on. It didn't. And then I smelled smoke, it's like some electric cord or something. So the alarm went off, so I just decided to come down," she said.

Firefighters said most of the people in the building at the time didn't act like Farquason, however, and instead ignored the alarm and stayed in their units.

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The building is expected to remain without electricity until Tuesday, which could require a total evacuation. (CBC)

Even though the fire was extinguished within a couple of hours, because of extreme heat conditions and the expectation power won't be restored until Tuesday, part of the building was evacuated, Fire Chief Ian Wade cautioned.

"So the power's been shut off. We've got any of the occupants that wanted to be removed have been removed and brought down and are presently in an OC Transpo bus, and we're just trying to get to the bottom of the problem," Wade said.

Residents are being encouraged to spend the night at the Canterbury Community Centre – or to make arrangements to stay elsewhere.

OC Transpo buses are taking residents to the community centre.