Authorities have revised down warnings of a possible tsunami that were in place in the early hours of Tuesday along the Canadian and US west coast.

Alarm was raised after a quake hit around 250 km (160 miles) southeast of Chiniak, Alaska at a depth of 25 km at 9.31am GMT, the US Geological Survey said. It initially said the earthquake had a magnitude of 8.2.

A red tsunami alert was in place for a large part of coastal Alaska and Canada’s British Columbia, but was later downgraded to an advisory after it was confirmed the wave heading for the coast was less than a foot high.

The remainder of the US west coast had been placed under under a tsunami watch, but this was cancelled as the scale of the tsunami became apparent.

Authorities expected the tsunami to hit the small fishing centre of Kodiak, Alaska, first. Kodiak has an estimated population of around 6,000 people.

Tsunami sirens sounded and residents were evacuated in the middle of the night.

In a warning for Alaska and British Columbia, Anchorage Office of Emergency Management said: “If you are located in this coastal area, move inland to higher ground. Tsunami warnings mean that a tsunami with significant inundation is possible or is already occurring.”

The NWS Pacific Tsunami Warning Centre said ”widespread hazardous tsunami waves were possible”.

Warnings from the NWS sent to mobile phones in Alaska said: “Emergency Alert. Tsunami danger on the coast. Go to high ground or move inland.”

People took to social media to say they had been told to evacuate.

“I just found out that I’m in the danger zone for a tsunami after a 8.2-earthquake and we got a warning call and have to evacuate with our horses and I’m so scared I can’t stop shaking,” one west coast resident said.

People said they felt the quake hundreds of miles away in Anchorage.

Alaska Governor Bill Walker said in a statement on Twitter that a blackout at the University of Alaska Fairbanks was making it more difficult to respond to the event.

A number of government tsunami-monitoring websites were not working on Tuesday morning, adding to confusion. It was not immediately clear whether this was associated with a federal government shutdown over the weekend.