One of Winnipeg's busiest shelters had to be evacuated Tuesday evening due to a carbon monoxide alarm. 

Just before 6 p.m., crews responded to the Main Street Project for reports of a potential fire. 

When firefighters arrived at the scene, they quickly found out it was not a fire and that the alarms had been triggered by carbon monoxide.

Firefighters quickly evacuated the building. A transit bus was set up at the scene to provide shelter to evacuees.

Paramedics assessed two individuals at the scene. They were transported to hospital, one in stable condition and the other in unstable condition. Their conditions were not believed to be related to the carbon monoxide.

The Winnipeg Fire Paramedic Service says the buildup of carbon monoxide is believed to have been caused by the use of diesel-fueled construction equipment in the building.