At 3:11 p.m., Orland Park police were called to the school by staff members after a student found what he or she believed to be a grenade. The Sandburg school buses were immediately evacuated and the area was cordoned off, police say.
The Cook County Sheriff's Police Bomb Squad brought bomb-sniffing dogs to the school and determined the grenade was a replica and "considered inert." All the school buses were searched, and no other suspicious items were found.
Regular bus routes resumed around 4 p.m.
Police say they received no bomb threats, and the school was never on lockdown.