Montreal firefighters spent much of Sunday evening battling flames at a condominium complex in Pierrefonds.

The fire department responded to a call at around 5:30 p.m. on Ceres Ave.

According to operations chief Martin Galarneau, the fire started on the roof of the six-unit building, spreading across the roof and also spreading to one of the units’ back decks.

At least 75 firefighters worked to extinguish the flames under sweltering conditions. Three firefighters suffered heat stroke and had to be transported to hospital.

Galarneau said it was a difficult operation.

“Since the roof was entirely engulfed, we had to remove our firefighters from the roof and then the roof collapsed from the third floor,” he explained. “We were able to get back to the third floor to fight the fires and there were no injuries to tenants of the building.”

Six families were evacuated from the building. The Red Cross and Urgences Sante were dispatched to the scene however there were no injuries among any of the residents.

An investigation is ongoing and although it appears to be accidental, the exact cause of the fire is not yet known.