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Devastating tornadoes that ripped across southern Ontario left a small town mourning an 11-year-old boy's death and hundreds of Toronto-area families displaced Friday from homes so badly damaged that they'll likely be torn down.

Several communities bore the brunt of the furious storm Thursday that spawned as many as four twisters and destroyed numerous buildings, ripped up trees, flipped cars and left thousands of people without power.

Dazed residents across the province were left surveying the damage from the storm, the latest in a line of intense weather events this summer that have seen a woman and two boys struck by lightning in a Brampton, Ont., park and three American tourists killed in northern Ontario by a tornado.

The terrifying spectacle of destruction came as Eastern Canada prepared for Hurricane Bill, which will most likely enter Atlantic Canadian waters this weekend packing winds of at least 150 kilometres per hour.

The lone fatality from Thursday's storm was the 11-year-old boy, who was killed when a tornado tore through a conservation area near the southwestern Ontario town of Durham, where children were at a day camp.

Mike Muir, Grey County EMS manager, said the majority of emergency resources were sent to the Saugeen Conservation Area, "where a number of injuries occurred."

"Those injuries were as a direct result of the storm and the storm damage, with buildings collapsing as well as debris flying around the area," Muir said.

"There was a day camp that was occurring at the time... There was a fatality at that location and it was a young 11-year-old boy."

The boy, whose name was not released, was from the Durham area and was killed by debris, police said.

Six other people were treated in hospital and released, the majority of the injuries being scrapes, cuts, bruises, and minor broken bones, a hospital spokeswoman said.

Acting Mayor Dan Sullivan said it would take months of work to remove the "scars" on the community, adding his town was in a recovery phase.

Only minutes after arriving at the industrial site where the worst damage had occurred in Durham, meteorologist Geoff Coulson confirmed with "no doubt" a tornado rated at least F2 on the Fujita scale had touched down, meaning winds were roaring upwards of 180 to 240 km an hour.

He estimated the damage occurred in a "matter of seconds."

"The worst of these things can be very, very brief, but it's very, very intense," he said.

In one of the hardest-hit neighbourhoods in Vaughan, north of Toronto, stunned residents gathered early Friday to survey the tornado damage.

Mayor Linda Jackson called it a "real miracle" that no one in the city was killed or seriously injured.

Still, the devastation was widespread. Some 200 homes were so badly damaged that they will likely be demolished, said Jackson, who added 600 additional homes were also damaged.

Fourteen building inspectors were surveying four storm-ravaged areas of the city.

A man evacuated from his home suffered a heart attack Friday morning after spending the night with his family and was in a coma, police said.

On Vaughan's streets, neighbours traded stories and cleaned up what they could.

Carm Spinelli was in her living room when the storm hit and has been staying with relatives because she hasn't been allowed back.

"It was a big roar. I never heard anything like that in my life," said Spinelli, who moved from the room just before her roof caved in.

"When I actually came outside and saw all of that I actually went into shock."

She, like other residents, said her next step is to talk to her insurance company about fixing the damage.

"You don't expect it, you never see this in Toronto, here," she said.

"We've had bad rain but not like this. It's not a good feeling."

Several streets of a residential neighbourhood were closed by police, but those allowed back in said they had never seen anything like this in Canada.

Pieces of trees, fences and brick were strewn across streets. Some houses had gaping holes in their front yards and exposed roof beams, while others were untouched by the storm.

Lampposts were torn off one driveway, while another was covered with downed trees, which had flattened cars, smashed lights and windows.

Fiorina Caravaggio was cleaning up after dinner when her granddaughter alerted her to the storm.

"I couldn't sleep last night. I never slept," said the distraught woman, whose home had broken windows and doors.

An evacuation centre in the neighbourhood was quiet, as many people in the tight-knit community opted to stay with family or friends.

Environment Canada was also dispatching crews to confirm tornadoes in Newmarket and the Collingwood area.

The Vaughan-area damage also seems consistent with a level-two tornado on the Fujita scale, Coulson said.

In Durham, giant tufts of pink insulation, splintered boards and crushed aluminum siding coated the lawn outside a printing facility, fitness centre, furniture store and veterinarian clinic where the greatest structural damage occurred.

A large trampoline rested upside-down on the pavement in front of the gym.

Corey Harris and his wife, Jamie, had just picked up their six-month-old son, Robert, from childcare and were planning to go shopping Thursday afternoon when they spotted the storm.

"We got only got so far when we started seeing clouds touching the ground, and swirling. There were birds caught up in this cloud," said Harris.

"We saw blueboxes exploding in mid-air. Unreal. Winds. So we had to turn around and get out."

Longtime Durham resident Jon Eckhardt was in his house when "everything starting to blow, trees start to topple over and then I knew part of the house at the top had blown away because of all the debris coming down."

"That's when I headed for the basement."

Eckhardt emerged after the storm passed to find his barn completely gone, some of his neighbour's barn is in his yard, and bales of hay all around.

While central and southwestern Ontario bore the brunt of the storm's fury, areas to the north were also affected, Coulson added.

"We did get reports . . . west of Powassan, up in the North Bay area, of a significant track of damage through a wooded area," he said.

Both Durham and Vaughan declared states of emergency because of the widespread damage in those communities.

Hydro One crews have spent the night re-attaching downed power lines, which left some 69,000 homes and businesses in the dark at one point.

By Friday morning, power had been restored in many areas serviced by the utility.

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