Environment Canada meteorologists say a 10-kilometre area around the town of Calabogie, Ont., was hit during Monday's storm by a macroburst, a column of sinking air that swoops down over a large area.

Thousands of people in the area around Calabogie — about 100 kilometres west of Ottawa — are still without power after fallen trees knocked out power lines in the region.

Hydro One said it might take until Thursday before power is fully restored in the area.

Investigators were surveying damage on Tuesday in a number of regions in eastern Ontario where unconfirmed tornadoes were sighted.

But the survey teams found no evidence of tornadoes, which tend to leave a long corridor or convergent pattern of damage. Instead in the Calabogie region they found a wide area — about 10 kilometres — where most of the trees knocked down had fallen in the same direction.

Meteorologist Peter Kimbell said this was consistent with a macroburst, a larger version of the same phenomenon that collapsed the main stage at Ottawa's Bluesfest music festival last year.

Kimbell said the broad line of winds exceeding 100 kilometres an hour resulted in damage over a huge area, but was not a tornado.

Environment Canada survey teams also found evidence of smaller microbursts in the Mississippi Lake, Munster and Richmond areas and said damage further west near Golden Lake was also much smaller than at Calabogie.

The storms swept through a wide swath of eastern Ontario on Monday, knocking out power from Barry's Bay in the west to Cornwall and Alexandria in the east.

The federal weather agency had issued tornado warnings for several eastern Ontario communities west of Ottawa, including Smiths Falls, Lanark, Sharbot Lake, Barry's Bay, Killaloe, Renfrew, Arnprior, Calabogie and French River.

Last Tuesday, two tornadoes touched down in eastern Ontario after a similar group of storms rolled through the region. One hit the area of Athens, near Brockville, and another touched down around Summerstown, east of Cornwall.