ST. CHARLES, Ill. (CBS) — Classes are set to resume Friday at St. Charles North High School, in St. Charles, a day after a bullet found by a staff member in a school hallway, prompted administrators first to lock down the school, and then dismiss classes early.

As WBBM Newsradio’s Bob Roberts reports, students were forced to leave their backpacks in the sixth-hour classes, and told to exit the school at about 12:15 p.m. Thursday.

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LISTEN: WBBM Newsradio’s Bob Roberts reports

District 303 Supt. Don Schlomann also canceled afternoon extracurriculars. He said the school received no threats, and said dismissal occurred without incident.

Overnight, administrative staff went through student lockers and using X-ray wands on the backpacks. Federal Alcohol, Tobacco, Firearms and Explosives agents began arriving at about 4 p.m. Thursday with trained dogs to sniff through both classrooms and hallways.

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Classes are to resume on a normal schedule Friday with one exception — students will report first to the 6th hour classes from which they were dismissed.

Most students will simply pick up their backpacks and head for their first-hour classes. But Schlomann said any backpack deemed suspicious will be opened by an administrator in the presence of its owner.

Schlomann said he formulated the plan of action within an hour of the time the bullet was found. The school was first placed on a lockdown, and then administrators moved from classroom to classroom to give instructions and dismiss students.

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Approximately 2,000 students are enrolled at the school, at Illinois Route 31 and Red Gate Road in St. Charles.