Four people were taken to hospital after an office building was evacuated Tuesday afternoon due to a carbon monoxide leak.

Emergency workers were called to the business in the 500 block of 24th Avenue SW at about 4 p.m. when a 33-year-old woman lost consciousness temporarily. Other employees complained of an odour in the air. 

The fire department tested the air and found a high reading of carbon monoxide .

"It was determined that a portable generator on top of the building was the culprit," fire officials said in a release. "The generator was placed near the building's fresh-air intake, which eventually led to the accumulation of the gas inside."

Four people were taken to hospital in non-life threatening condition.