Investigators believe they know what sparked a devastating house fire in Innisfil.

Large flames could be seen jutting through the roof of the home on Big Bay Point Road, near Strathallan Woods Lane on Monday, at around 10 a.m. This is just outside of Barrie city limits.

Crews from Barrie and Innisfil helped knock the fire out. But the fight wasn’t without its challenges.

“Wind was making the fire even harder to put out once it was through the roof,” says Innisfil fire chief John Pegg.  

Two people who lived in the home made it out safely. Their three children were already in school. They rented the home.

Damage is estimated at $700,000, but fire officials say that amount could rise.

“It looks like the fire did start on the exterior of the home; looks like around the deck area. The home owner of the tenants did say they recently cleared out their fire place. So we're thinking hot ashes that were removed from the fire place on the deck,” says Pegg.

The Ontario Fire Marshall’s Office has been notified, but will not lead the investigation.

Pegg is expecting more calls about fires or flare-ups involving material from chimneys in the coming weeks.