(PUEBLO, Colo.) -- Eight people were reported injured Saturday after a furnace exploded at a Colorado steel mill, according to officials.
Firefighters received a call about the explosion at the Evraz Rocky Mountain Steel Plant in Pueblo, Colorado, around 6 p.m. local time, according to the Pueblo Fire Department. Assistant Fire Chief Keith Miller told Colorado Springs ABC affiliate KRDO-TV that an electric arc furnace, which is used to melt steel, exploded.
Firefighters found 130 tons of steel inside the furnace at max temperature and had to wait for the metal to cool down before they went in and operated, Miller said.
Fire from the exploded furnace was on three different levels of the building, according to Miller, who called the incident a "rare event."
Seven people were transported to area hospitals, three of whom were in critical condition, the fire department said.
On Sunday afternoon, Local 2102, the union representing the mill workers, said an additional worker went to the hospital on their own.
Five of the injured were treated and released, two were in the ICU and one of the victims was transferred to a burn unit in Denver, according to the union.
"Please keep them along with their families and those who witnessed the accident in your thoughts and prayers," Local 2102 wrote in a Facebook post.
The Pueblo Fire Department didn't immediately respond to ABC News on Sunday evening for more updates.
ABC News has reached out to the Evraz corporation for comment. David Light, the company's vice president of Pueblo operations, told KRDO it was investigating the incident.