Emergency crews had to evacuate a building in northwest Calgary on Wednesday morning after high levels of carbon monoxide were found a number of units.
Crews were called to the scene on Royal Birch Boulevard N.W. at about 7:20 a.m. after a carbon monoxide alarm went off.
About 50 people were evacuated and sheltered in Calgary Transit buses while crews ventilated the building and sought out the problem.
They eventually found that the vents on the roof had become covered in ice.
No one was affected by the leak and all residents were allowed to return home later in the morning.
