A mild tsunami has hit Hawaii after a powerful earthquake off the west coast of Canada, forcing a state-wide evacuation but apparently failing to cause major damage.
Television images from the island of Oahu showed relatively small waves peacefully rolling toward shore.
Shortly after, forecasters lifted a tsunami warning issued in the wake of the quake.
'Based on all available data the tsunami threat has decreased and is now at the advisory level and not expected to increase,' the Hawaii-based Pacific Tsunami Warning Center announced.
The centre warned, however, that sea level changes and strong currents could still occur and present a hazard for swimmers and boaters.
'The threat may continue for several hours,' the centre cautioned.
Highways and roads in coastal areas were reopened, allowing thousands of residents and hundreds of tourists to return to their homes and hotel rooms.
But the tsunami, set off by a powerful 7.7 magnitude earthquake that struck off the west coast of Canada, succeeded in disrupting the weekend activities of many tourists and residents.
Countless Halloween parties were interrupted, restaurants, bars and movie theatres emptied, and highways quickly filled with cars heading away from beach areas.
Tourists from Waikiki to Turtle Bay in Honolulu were evacuated to higher floors in their hotels, and major tourist centres looked abandoned for several hours.
Governor Neil Abercrombie declared a state of emergency when the first alert was sounded and kept it in force.
'We are taking a wait-and-see approach - we want everyone to be safe,' said the governor's spokesperson, Donalyn Dela Cruz.
Initially, the Pacific Tsunami Warning Center said there was no 'destructive widespread tsunami threat' after the 7.7 magnitude quake shook the Queen Charlotte Islands off the west coast of Canada.
But later it issued a warning, saying a tsunami had been generated by the earthquake and that it was headed toward Hawaii.
The epicentre of the Canadian quake, which occurred at 8.04pm on Saturday (1404 AEDT on Sunday) was located 139 kilometres south of the town of Masset, the US Geological Survey said.
Numerous aftershocks, some as strong as magnitude 4.6, followed the initial quake.
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.
'The tsunami alarm went off and everybody went to the evacuation site,' Danny Escott, owner of the Escott Sportfishing lodge near Masset, said by telephone.
But officials in Canada sought to calm the population.
Natural Resources Canada said in a statement that the quake was felt across much of north-central British Columbia, including Haida Gwaii as the Queen Charlotte Islands are also called, Prince Rupert, Quesnel and Houston.
But the ministry also played down the effects on Canada, saying: 'There have been no reports of damage at this time.'