Some people in Terrace, B.C., say they were awoken Thursday morning by some strange, whining and grinding noises echoing off nearby hills for several minutes, prompting a wide range of speculation online about the source.

At least three different people recorded the phenomenon, including Kimberly Wookey, who posted a video on YouTube.

Mandi Campbell described hearing the loud sounds rolling through the hills around the city

"It seemed to be coming from the sky or underground, something so loud though. And I believe it was heard in Hazelton, which is close to here, and as far as the Nass," said Campbell.

Initial speculation about the source of the sounds included last year's earthquake that struck northwestern B.C., or perhaps the 7.0 magnitude quake that struck off the Aleutian Islands on Friday morning.

But Honn Kao of the Geological Survey of Canada said the noise is not related to any seismic activity in the region.

Other popular theories included electromagnetic activity or a just a train, but residents insisted the noises aren't from the nearby train tracks.

Reports of strange sounds all around the world lit up the internet in 2011 as well, when they were dubbed "sky trumpets" by some.

City offers explanation

On Friday afternoon city spokesperson Alisa Thompson said she had a simpler explanation — it was a city worker grinding down the blade on a grader.

"The grader blade needed to be straightened. Kind of gets ground down, and it makes a very strange noise. It's as simple as that," said Thompson.

"The video, the YouTube video, is actually right around the corner from the arena, and that's where our employee was doing the straightening."

Thompson said the city will try to replicate the sound and prove it was the grader this afternoon, although she admits she likes the more creative explanations better.

"Like some kind of epic battle between a Kermode, and UFO, with sasquatch and maybe a whale thrown in there. That would be great for local tourism."