A midtown condo was evacuated early this morning after carbon monoxide was detected in the building.

Toronto Fire Capt. Adrian Ratushniak said crews were called to a building on Merton Street, located near Mount Pleasant Road and Davisville Avenue, shortly after 1:30 a.m. after a carbon monoxide detector went off.

The gas was detected at the penthouse level and all tenants were removed from the building.

No one was injured.

Enbridge was called to the scene and paramedics also responded as a precaution.

The problem was eventually traced to a roof-mounted HVAC unit that was malfunctioning.

Five TTC buses were called in to keep tenants warm in the frigid weather while crews worked to repair the unit and ventilate the building.

Residents were eventually allowed back into their units at around 5 a.m.