Fire completely destroys home on Crown Street in Thunder Bay, Ont.

A three-storey home on Crown Street in Thunder Bay, Ont., has been completely destroyed by a significant structure fire Sunday afternoon.

Members of Thunder Bay Fire Rescue responded to the scene near the intersection at Bay Street early Sunday afternoon after receiving a call about a possible explosion.

"We could see a large plume of smoke initially right after the call, and had units on scene really quickly," said platoon chief Stephen Vincent on the scene.

Three people were treated at the hospital as a result of the incident, he said. No firefighter injuries have been reported.

A CBC News reporter on scene witnessed at least half a dozen fire trucks along Crown Street responding to the blaze, as well as members of the Thunder Bay Police Service and Enbridge Gas. Firefighters were seen dousing the remnants of the single-family dwelling from the balcony of an adjacent residence. 

Debris was scattered around the property, along with shards of glass on the sidewalk across the street. Dozens of neighbours watched fire crews respond, many of which were observing from Hillcrest Park. Black smoke could be seen from Memorial Avenue, witnesses told CBC News.

The cause of the blaze has not been confirmed, said Vincent.

"Due to the extent of the fire and the buildings on both sides, we called the third alarm, which emptied the city of resources," he said. "We had individuals called in on their time off to man trucks, so that we can still respond in town."

The Office of the Fire Marshal has been notified and will likely be involved in the investigation, Vincent said.

Power and gas were shut off on the block as a precaution. Just after 2 p.m. ET, Vincent said those services would be restored shortly.