An explosion at a Wisconsin oil refinery has left at least 20 people injured.
The blast occured at the Husky oil refinery in the east end of the city of Superior, near the state border.
Witnesses reported a “sonic boom” at around 10am local time, with buildings shaking one mile from the scene.
Buildings at the refinery, which employs 180 people, were evacuated as workers attempted to get upwind from huge plumes of smoke.
Officials said at least 20 people were hurt, with five taken to hospital. No fatalities have been reported.
One nearby worker told Duluth News Tribune: “It shook the houses all over. They felt it at Belknap Plaza.
“Tons of people were trying to get down there. They should be staying out.
“They had people evacuating, a lot of the contractors. They are trying to get upwind of the smoke.
“I’ve seen at least eight ambulances go in there and six fire trucks.”
Police have urged people to avoid the area.
The Superior Fire Department said “at least” 20 people have been injured.
Superior Fire Chief Steve Panger said: “There is a report of multiple casualties. Initial reports are at least 20 casualties transported. Multiple agencies have responded.”
Officials said they did not believe any casualties had been reported.
They later said five people had been hospitalised. Others suffered from minor injuries.
A spokesman for the City of Duluth, which lies across the Saint Louis Bay and River from Superior, said: “The City of Duluth is saddened to hear of the explosion at the Husky refinery in Superior, Wisconsin.
“The City of Duluth, and the Duluth Fire Department, have offered assistance and remain on standby should the Superior Fire Department need it.
“The two cities, and Mayors Paine and Larson, have been and remain in communication.
“This situation is ongoing and developing. The Superior Fire Department has operational control of the situation, and all questions should be directed to them.”
Electrical crews were carrying out construction work at the time of the blast, which officials say meant the refinery was busier than usual.
St Luke’s Hospital in nearby Duluth said a command centre had been established to deal with injuries.
A spokesman said: “St Luke’s has set up an incident command centre and we are fully prepared to receive patients from the explosion at the refinery in Superior.
“We will continue to keep you informed as the situation evolves.”