(OAK PARK)  Nearly 600 students in the Oak Park Elementary School District were absent because of illness Monday.

The school district, which announced the absences on its website Monday, said it will be “monitoring this situation closely during the next 24 to 48 hours.”

The district’s custodial staff will also be performing a “thorough and extensive” cleaning of all building surfaces, the district said.

Officials suggest that students who exhibit cold and flu-like symptoms, such as a fever of 100 degrees or higher, not return to school until they are symptom-free for 24 hours.

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