Demolition crews have begun tearing down a commercial building on Queen Street destroyed by fire early Tuesday morning.

Witnesses told emergency officials they heard what sounded like explosions before flames erupted above the Roots store, located at 369 Queen St. W., before 1 a.m.  

“[Investigators] have been able to confirm that we did have an explosion here,” Jeff Minten, of the Ontario Fire Marshal’s Office, told CP24 at the scene Tuesday evening.

Minten said investigators are now trying to determine which came first – the explosion or the fire.

The three-alarm blaze gutted the building that was also home to a hair dresser and a tattoo parlour.

“Our investigators are looking at everything coming out,” Minten said of the demolition. “What they’re looking for is potential fuel sources.”

Minten said that crews will continue working through the night in an effort to get Queen Street open as soon as possible.

“As soon as we can open those lanes is probably when we’ll shut down and get a little bit of rest,” he said.

Earlier Tuesday, a woman who lives across the street from the fire told CP24 that her apartment shook and when she looked out the window, she saw flames shooting out of the building.

"It's safe to say it's not storm related," Eric Cotter, of Toronto Fire Services, said.

A hole measuring approximately seven-feet in width could be seen at the front of the building, above the Roots sign. Across the street, on the north side of Queen Street, garbage and leaves were strewn across the sidewalk and roadway.

Though people live in the adjacent building, above the Peter Pan restaurant, Cotter said no one was injured in the blast.

However, the neighbouring building did sustain smoke and water damage.

At one point, officials moved spectators back from the fire scene as they feared the Roots building would collapse.

The Fire Marshal’s Office continues to investigate the cause of the blaze.

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