An explosion outside a floor and window coverings shop in Winnipeg's St. Boniface neighbourhood has sent a man to hospital in critical condition and caused considerable damage to vehicles and a trailer.

Emergency crews were called at about 9:30 a.m. to Ken's Carpets and Urban Home Style Centre at 730 Archibald St.

Joe St. Laurent, a warehouse manager at Ken's Carpets, was critically injured in an explosion behind the building on Monday. (Courtesy Ken's Carpets) "I was sitting at my desk working and heard a very loud boom. My entire house shook quite violently," said Sarah Piercy, who lives on Lariviere Street, not far from the scene.

"I actually thought a tree had fallen on our house."

A crumpled and charred metal container believed to have been used for storage was found at the site of the blast.

Doug Martin, a platoon chief with the fire service, said it was fortunate that the explosion and fire occurred in an open area, though he described the damage as "extensive".

"There was no involvement of the actual store or that sort of thing and there really is nothing else in close proximity so that's the good news about that."

"Upon their arrival they found a pretty good fire in the back. It involved a semi-trailer and there was one individual that was injured, a male, he was transported to hospital by paramedics in critical condition. "

Martin said the damaged container appeared to be a storage facility containing carpets and other items.

"There was no damage to the building but there was damage to the vehicles that were parked in the rear and as well as to the trailer," he said.

Some type of metal storage container is crumpled and charred after Monday's blast. (Jaison Empson/CBC) The cause of the fire and explosion, he said, is now under investigation by the arson strike force and the office of the fire commissioner.

Ken's Carpets released a statement Monday afternoon, saying, "We are shocked by the unexpected accident that took place today in our back parking lot. At this time we are most concerned about our employee who was injured in the accident and our thoughts and prayers are with him and his family at this time."

The man who was injured, 55-year-old Joe St. Laurent, was a warehouse manager for the company

The statement added the company is waiting for word from the fire department.

According to witnesses, St. Laurent was outside smoking a cigarette when he went to get something from a storage container behind the store. When he opened the door, the container blew up.

His legs were badly burned in the explosion.

The province confirmed that a BBQ propane tank near the storage locker was the source of the explosion.

'Felt the building shake'

Dave Jeanson, who works about six blocks away at ABS Fire and Safety on Marion Street said staff at his company were in a meeting when they "felt the building shake. So I went outside and didn't see anything so I went up on the roof and saw all the black smoke."

Jeanson said he believed the damaged container was a simple container "that people use to store stuff. We have one of them at our shop as well. They're inexpensive to buy and people use it for storage so I'm not sure what was stored in there."

Peter Izokun works nearby. He said he felt the blast and saw a huge plume of black smoke.

"All the house was shaking," he said. "I was scared. It was a very loud boom … then I just came out," he said.

According to a city spokeswoman, the fire extended to the exterior of the building but was extinguished by 10 a.m.

Whatever the investigation turns up, Jeanson said the effect was spectacular.

"A big explosion," he told the CBC. "Yeah, just like you see in the movies. Just boom and shook the whole building."