Residents of Superior, Wisconsin can finally return home after being evacuated for more than 12 hours on Thursday.
The massive blaze that engulfed the Husky Energy oil refinery at the southeast end of town led to an evacuation order on Thursday afternoon, as noxious fumes invaded the area surrounding it.
Although the fire was extinguished at 6:40 p.m., officials determined it wasn't safe to allow people back to their homes until 6 a.m. Friday.
Residents within a three mile radius of the refinery and 10 miles to the south – the direction the smoke was blowing – were included in the evacuation area.
Some of those living in nearby Duluth meanwhile were under a "stay-in-place" advisory overnight, which has also been lifted.
Superior Mayor Jim Paine said on Facebook: "All indications are that the refinery site is safe and stable and the air quality is clean and normal. Welcome home."
Investigators assess the aftermath
While there were around a dozen reported injuries, nobody was killed in the blasts.
One of those on the site told the Duluth News Tribune that most workers were on their break when the explosion happened.
Authorities and refinery officials will now begin the process of assessing the damage to the facility, which at its peak can produce 50,000 barrels of oil per day from Bakken and Canada, and serves the Northland area with petroleum products.
The blaze sent a huge plume of acrid, black smoke into the air, viewable from miles around, while images from the scene at one point showed oil gushing from one of the refinery's containers.
Husky Energy told the Star Tribune that the initial explosion happened in the "catalytic cracking area" of the refinery, which is where heat is applied to crude oil to extract gasoline.
Federal investigators are among those on site, along with local and state officials to determine what caused the explosion.