Roads are blocked off around the refinery, and employees have been evacuated. Superior police ordered an evacuation for anyone located 10 miles to the south of the refinery, three miles to the east and west, and one mile to the north.
Evacuees are being told to gather at Yellowjacket Union at the University of Wisconsin-Superior or at Four Corners Elementary School in Superior.
It was unclear how many people were being evacuated. The corridor downwind to the south is sparsely populated. Superior is a city of about 27,000 people that borders Minnesota to the north and the tip of Lake Superior. Essentia Health is transferring its patients to St. Mary's in Duluth.
Talarico says another five are being treated at St. Mary's Hospital in Superior, Wisconsin, where the explosion happened. The other nine injuries are not life-threatening, she said.
Officials from St. Luke's say they have received one patient and are not expecting to receive anymore. She did not have a condition for that person.
The fire department said "multiple casualties" have been reported and "at least six transported".
A tank containing crude oil or asphalt exploded at a large refinery in Wisconsin on Thursday, injuring several people and causing a blast that one worker described as sounding like a sonic boom. U.S. Department of Labor spokesman Scott Allen said the Occupational Safety and Health Administration fined Calumet Superior LLC $21,000 over emergency response and flammable liquids violations in 2015. Officials say the fire could be burning for days, as it cannot be easily extinguished.More news: Grassley Pushes Back at McConnell's Effort to Block Mueller Bill
There are no other details of the extent of the injuries or how many, or how many casualties there are at this time. The fire is out.
A contractor who was inside the building told WDIO television that the explosion sounded like "a sonic boom" and that it happened when crews were working on shutting the plant down for repairs.
Reports of an explosion and fire at the Husky Energy refinery emerged just after 10am on Thursday.
Five people were taken to hospitals in Duluth, Minnesota, Panger told AP. There are no known fatalities.
Panger added the explosion was reportedly from a small tank explosion, and the product is believed to be crude or asphalt.
Husky Energy, who purchased the refinery in November, employs about 180 people. There have been no neighbourhood evacuations.