A magnitude-6.4 earthquake struck off the coast of Vancouver Island on Friday afternoon, sending out tremors that were felt hundreds of kilometres away.

According to the United States Geological Survey, the quake, which was initially measured as a magnitude 6.7 tremor, hit at 12:41 p.m. local time.

The epicentre was a point 23 kilometres underground, south of Port Hardy about 50 kilometres off Vancouver Island's west coast.

The exact magnitude of the quake was revised later in the day as seismologists in Canada and the U.S. analyzed data collected from the temblor. A number of smaller aftershocks followed.

There were no immediate reports of damage, and no tsunami was expected from the quake according to the Pacific Tsunami Warning Centre.

Residents as far south as Seattle and as far east as Kelowna, B.C. reported feeling the quake.

"It has been widely felt -- mild swaying -- but there are no reports of damage or injuries anywhere," said Heather Lyle, who runs province-wide earthquake drills with Emergency Management BC.

One of the closest communities to the epicentre was the tiny town of Tahsis on the west coast of Vancouver Island, where Captain Meares Elementary Secondary was evacuated as residents felt their homes shake.

Silvie Keen, the chef and owner of Nootka Gold Bed and Breakfast, told ctvbc.ca that she lost power for about five minutes.

"It was a little scary. The dog and I went under the table," she said. "It was long. It seemed like about 15 seconds, and the house was a little bouncy."

Keith Pistell was working at the Canadian Tire in Courtenay, on the island's east coast, when the quake hit.

"I really started moving, and you could feel the walls of the building started to shake," he said.

Meanwhile in Vancouver, more than 270 kilometres east of the quake's epicentre, CTV's Sarah Galashan reported that workers in her office building "could feel a little bit of movement."

Some residents in Richmond, B.C., also felt the quake, she said.

Paul Laustsen, a spokesperson with the USGS, said an earthquake of this magnitude would typically cause "moderate to heavy shaking."

Depending on how long the shaking lasted, "it could feel like a truck hitting the side of a home," he told CTV News Channel.

Several fault lines run through the area, Laustsen said, from California north to Alaska.

By late Friday afternoon there had already been a half-dozen aftershocks, with the strongest reaching a magnitude of 4.9.

In Victoria, seismologist John Cassidy said the aftershocks could continue for the next week.

"An earthquake of this size we see typically every decade or so, and generally in the offshore region," he said by phone. "This is a very seismically active zone."

With files from CTV Vancouver Island's Gord Kurbis and The Canadian Press