CHARLESTON, Ill. (AP) — Eastern Illinois University officials say they will investigate the cause of a fire inside a three-story heat-recovery unit at the school’s Renewable Energy Center. Charleston Fire Chief Pat Goodwin said the fire Tuesday night took several hours to put out because it was inside the structure and spread to a boiler. Goodwin said one firefighter suffered minor burns. University officials say they don’t plan to start investigating the cause of the fire until Monday because they have to wait for 18-inch-thick bricks that are part of the heat-recovery unit to cool. The university says the center continues to function and produce steam for energy production.