A vacant, boarded up home in Waterbury collapsed as firefighters were responding on Thursday morning.
The fire at the three-story wooden home 309 Bishop St. was reported around 8:30 a.m. and was upgraded to two alarms.
It is being called suspicious because it has been vacant for years and was secured, with plywood on the windows and doors.
Arson investigators have dogs at the scene to help determine if the fire that caused the building to collapse in 20 minutes was set.
Eight firefighters were on the roof and porches when a side of the building came down, but no injuries are reported.
The smoke was so heavy that it was seen from miles away.
