Dozens of children were transported to area hospitals Friday after a malfunctioning boiler apparently released carbon monoxide fumes into an elementary school on Chicago's Northwest Side.
Fire department officials said 71 children and eight adults were treated for signs of carbon monoxide poisoning.
Ernst Prussing Elementary School was evacuated for "abnormally high" carbon monoxide levels after several kids complained of feeling ill.
Fire officials responded to a level one Hazmat situation at 4650 N. Menard. The school self-evacuated and 12 ambulances were called to the scene, according to Chicago Fire Department spokesman Larry Langford.
Langford said a likely cause for high carbon monoxide readings was the school's furnace.
The incident happened shortly after the school's Halloween parade and many kids were still in costume when the school was evacuated.
The school planned to test the furnace Friday afternoon.
