Five St. Paul firefighters were being treated for heat exhaustion while fighting a fire at a vacant commercial building, authorities said.
St. Paul Fire Marshal Steve Zaccard said firefighters responded to a two-alarm fire at 327 Fisk St. at 9:23 a.m.
Four of the firefighters were taken to Regions Hospital, where they were expected to be released soon. A fifth was treated at the scene.
Zaccard said the fire was stubborn and labor intensive.
"Inside it's several hundred, a thousand degrees," Zaccard said. "It had gotten in the walls and ceilings, and to attack the fire we have to open up the walls and ceilings to put water on the fire. So that's very difficult work."
Zaccard said investigators are still on the scene looking for clues as to what caused the fire. He said the building was vacant and secure when they arrived.