Residents of two highrise apartment buildings in Victoria Park were allowed to return after being evacuated early this morning due to carbon monoxide.

Fire crews responded to the call at about 3:00 a.m. Residents were alerted by alarms in the buildings and a voice over the loudspeaker telling them to evacuate, and most were out by 4:00 a.m.Most didn't know why until they got outside.

Some of the residents were allowed to retrieve their vehicles from the underground parkade, while most people were moved to the BMO Centre to keep warm. No one was injured, but paramedics checked a few people out to be sure.

Crews discovered a vent on the roof of the building was blocked with snow, trapping the carbon monoxide inside the building. At one point, the concentration of the gas was at 100 parts per million, a dangerously high level.

“Anything over 10 to 12 parts per million, we start to get concerned, so 100 parts is quite high,” said Dist. Chief Bruce Gelhorn, Calgary Fire Department.

The buildings are being ventilated and residents are starting to return to the north tower.