TORONTO (Reuters)—Insurers began to assess the damage Friday after tornadoes and violent thunderstorms struck southern Ontario late Thursday, killing one person and destroying homes, businesses and cars.

It is too early to put a value on the damage rendered by the winds, hail, rain and flying debris. Property owners are expected to take several days to assess their losses and file claims, insurers say.

"We're starting to see some claims come in, in a fairly steady way," said Ian Blair, a spokesman for Intact Financial Corp, one of Canada's largest property and casualty insurers. "Primarily it's wind damage as you might expect, as opposed to rain damage."

As many as four tornadoes reportedly touched down in southern Ontario, north and west of the provincial capital of Toronto, early on Thursday evening.

Environment Canada confirmed at least one tornado touched down and was investigating other reports of tornado and funnel cloud sightings, as well as reports of flipped cars, destroyed buildings and uprooted trees in communities across the southern part of the province. Some flooding was also reported.

There were dozens of unconfirmed reports of funnel clouds traveling through the central core of Toronto, Canada's largest city.

"There were probably four, or at least four, but it is too early to confirm with certainty," said Peter Kimbell, a meteorologist at Environment Canada. He said five teams were out investigating damage across the region.

There was one reported death of an 11-year-old boy who was camping at a conservation area near the small town of Durham, Ontario, northwest of Toronto, as well as numerous injuries.

A spokeswoman for the Insurance Bureau of Canada, an industry association, said most of the damage is likely covered by homeowner policies and by comprehensive auto coverage.

"Most of the stuff that happened last night should be covered," said Nikki Holland, manager of government relations at the IBC.

Damage from falling trees and water entering homes through roofs or windows damaged by the storm are typically covered by property insurance, Ms. Holland said, but noted that "overland flooding"—where water comes into homes from ground sources—is not typically covered.

Intact Financial's Mr. Blair said he expected steady claims to be reported for several days because the tornadoes hit the district near Lake Huron and Georgian Bay, where many Torontonians have second homes. Because they are often unoccupied during the week, policyholders may not yet know the building's are damaged.

"We expect to see more (claims) come in over the weekend and early next week as people get up to their cottages, because as you know a lot of the damage zone is in cottage country."