Twelve people have been hospitalized after a carbon monoxide leak at an apartment building in Skokie.
Police said a resident called 911 around 2:30 a.m. Thursday and reported feeling ill.
Responding emergency officials detected high levels of carbon monoxide. Firefighters had to break into some apartments to help residents get out.
The conditions of those taken to hospitals were not immediately known.
Skokie fire Capt. Steven Ludkowski said it is not yet clear what caused the high levels of carbon monoxide. He reminded the public to be sure their carbon monoxide detectors are working and to have their furnaces checked.