Police have not found the source of the leak or confirmed what it is.
Two teachers and 24 students reported feeling lightheaded and were taken to a hospital from Noel LeVasseur School at 601 West Bethel Drive. Those teachers and students were in two separate, adjacent classrooms.
The school was evacuated. Students were taken to Liberty School where parents were directed to pick up their children at regular dismissal time.
Bourbonnais superintendent of schools Daniel Hollowell said the fire department found no signs of any gas or odor on their meters.