Firefighters in Innisfil are trying to determine what may have caused a fire at a century-old Victorian home.

Crews were called to the house on Sideroad 5, between Innisfil Beach Road and 6th Line, around 9:20 a.m. on Sunday.

They arrived to find smoke billowing out of the chimney, and flames spread to the home’s upper floor and attic.

Investigators say they have no reason to believe the fire is suspicious in nature, but crews did have some challenges gaining access to the fire.

“There are very small holes to get into the attic, so you have to pull some ceiling down. It becomes very involved, and creates more damage to the house, unfortunately. There’s just no other way to get into that fire,” Innisfil Fire Deputy Chief Tom Raeburn told CTV Barrie.

Raeburn also adds the home did have working smoke alarms, but they were not activated.