A garage collapsed at a home just outside Arnprior after Friday's storm. (Submitted by Robin Paquette)

Uprooted trees and other damage in the Petawawa, Ont., region during Friday's storm was likely caused by a fast-moving column of air called a microburst, according to an Environment Canada investigator.

Much of eastern Ontario and parts of west Quebec were under a tornado watch Friday as the storm front rolled through the region.

But Peter Kimbell said his preliminary investigation showed most of the trees damaged or uprooted appear to have all fallen in the same northeast direction, suggesting a large microburst, and not a tornado.

A microburst is a column of sinking air that can come down at speeds over 100 kilometres per hour.

"When those downdrafts hit the ground they can do damage just like a tornado," said Kimbell.

The storm uprooted trees and sheered thousands of tree branches, knocking out power to much of the community. One mall had a long section of roof ripped off its frame, though no one was inside the building at the time.

"Rain was coming at you sideways with a ferocious wind coming up and just an absolutely scary environment," said Petawawa mayor Bob Sweet.

Woman dies in Montreal area

One woman died during the storm after she was struck by a falling tree branch at a pool in Boucherville, Que., on Montreal's south shore.

There were no serious injuries reported in the Ottawa region.

Hydro One said it has restored power to about 100,000 households in central, north and eastern Ontario but that 93,000 customers remained without power as of Saturday afternoon.

Notable regions still without power included Kingston, where some 8,400 customers were without power Saturday, and Cobden, Ont., where another 6,300 customers were also waiting on repairs.

About 900 Hydro Ottawa customers who were without power Saturday morning have since had their power restored.

Just under 18,000 people in the Outaouais region were also without power as of Saturday at 4 p.m., according to Hydro Quebec.