The school district said they received a threatening message directed at Kolmar School.
Oak Lawn police are investigating the "specific and serious threat," officials said.
The school district said in a statement, "We know this kind of message is upsetting. Our priority is the safety of students and staff, and we will continue to communicate clearly as we learn more. We will send another update later today, even if the investigation is still ongoing."
Oak Lawn police said they identified a person of interest and sent additional resources to local schools.
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Police said the person has been cooperative. It appears a suspect or suspects used the person's identity in a "swatting" incident.
The threat is currently considered unsubstantiated, police said.
Police continue to investigate.
All weekend activities and events at district schools are canceled and will be rescheduled at a later date.