Crews are fighting a major fire at the Irving Oil refinery in Saint John, New Brunswick.
CBC News reports people nearby reported a "bed shaking explosion" and police are urging people to avoid the area.
Meanwhile, eyewitnesses have taken to social media to post images of black smoke rising from an area inside the refinery.
At this hour, it's unknown if there are injuries.
Irving Oil exports more than half of that to the United States, and the refinery is a critical source of fuel for the Northeast energy market, CNBC reported.
He said there had been a problem with the refinery's diesel treating unit, which removes sulphur from diesel fuel, but it wasn't yet clear exactly what caused the malfunction.
Compounding the issue is aging infrastructure, which Tucker said has led to a major fire or explosion occurring in Canada "every two years or so".
"I heard a loud bang that shook our house and rattled the windows", said Gordon Dalzell, who lives in Saint John near the refinery.
The thick, black plume of smoke earlier in the day had been cause for concern for Gordon Dalzell, who lives in the nearby subdivision of Chaplain Heights - but the bigger issue, he said, is the other pollutants in the air that can be neither seen nor smelled.
Irving Oil tweeted out that all workers and personnel have been accounted for, adding there were no serious injuries.
He chose to drive by the refinery and said he was nearby when he felt the vibrations of what he assumes must have been a second explosion.
Nate Guimond, 36, said he was doing house repairs when he saw smoke.
Irving says on Twitter that they are "actively assessing the situation" and they will share more information when it becomes available.
He made a decision to drive by the refinery, and said he was nearby when he felt the vibrations of what he assumed must be a second explosion.
When he walked outside, he noticed black smoke coming from the refinery, so he hopped into the vehicle, drove down the corner and saw fire about 30 metres high. "We will update as soon as we have more information".