A major 7.7 magnitude earthquake shook the Queen Charlotte Islands off the west coast of Canada late Saturday, triggering a potentially destructive Pacific tsunami that is now headed toward the US state of Hawaii.

The epicenter of the tremor, which occurred at 8:04 pm (0304 GMT Sunday) was located 139 kilometers (86 miles) south of the town of Masset, the US Geological Survey said.

Numerous aftershocks, some as large as magnitude 4.6, followed the initial quake, Canadian officials reported.

Initially, the Pacific Tsunami Warning Center said there was no "destructive widespread tsunami threat" at this time.

But later it issued a warning, saying a tsunami had been generated by an earthquake off the west coast of Canada and is headed toward the US state of Hawaii, the Pacific Tsunami Warning Center announced early Sunday.

The tsunami "could cause damage along the coastline of all islands in the state of Hawaii," the center said, adding that "urgent action should be taken to protect lives and property."

The expected arrival time of the tsunami is 10:28 pm local time Saturday (0828 GMT Sunday).

"Initial reports indicate that a wave of around three feet (one meter) is anticipated, with Kahului likely to be impacted by a larger wave, possibly up to six feet (two meters)," Honolulu's KITV station said.

Meanwhile, emergency officials in British Columbia urged residents in low-lying coastal areas to be alert to instructions from local officials and be prepared to move to higher ground.

Some actually did. "The tsunami alarm went off and everybody went to the evacuation site," Danny Escott, owner of the Escott Sportfishing lodge near Massett, told AFP by telephone.

But overall, officials in Canada moved to quiet the population.

"We would not be expecting any widespread damage or inundation," Kelli Kryzanowski of Emergency Management British Columbia told reporters early Sunday during a teleconference.

Natural Resources Canada said in a statement that the temblor was felt across much of north-central British Columbia, including Haida Gwaii as the Queen Charlotte Islands are otherwise called, Prince Rupert, Quesnel, and Houston.

But it, too, played down the tremor's effects on Canada.

"There have been no reports of damage at this time," the ministry said.

However, experts said temblors exceeding magnitude 7.0 were extremely dangerous.

"A 7.7 is a big, hefty earthquake. It's not something you can ignore," Gerard Fryer, senior geophysicist at the Pacific Tsunami Warning Center told n CNN International.

He explained that the latest tremor had occurred partly under an island, but mostly under shallow water.

"I think we have to be thankful it happened where it did," Fryer said. "If that were a heavily populated area, it would have caused significant damage."

"It definitely would have done significant damage if it had been under a city," the geophysicist added.

The earthquake reading was based on the open-ended Moment Magnitude scale used by US seismologists, which measures the area of the fault that ruptured and the total energy released.

The Queen Charlotte Islands, which are also known by their official indigenous name of Haida Gwaii, comprise about 150 islands located north of Canada's Vancouver Island. Their total population is about 5,000. The Haida people make up about 45 percent of the total population.