The building where four people were found in the underground garage suffering the effects of carbon monoxide, was a building under construction. There were no residents occupying the building.

The initial cause of the CO2 in the underground parking area is thought to be from a concrete power trowel that was being operated inside the building.

The Saskatoon Fire Department was called out to the 100 block of Horner Crescent in Evergreen at 5:58 p.m. Thursday.

When they arrived, firefighters discovered one person suffering the effects from carbon monoxide. Crews put on their breathing apparatus and searched the underground parking garage locating three more patients. All patients were transported to hospital by ambulance.

Fans were set up to ventilate the underground garage. The investigation has been turned over to Saskatchewan Occupational Health and Safety.