The Geneva school district conducted a drill Friday afternoon at Geneva Middle School South to test the emergency response skills of school workers, police officers, firefighters and Delnor Hospital workers.
Students were dismissed at 10:26 a.m. and not involved in the drill, according to the district.
The drill started at noon with an "explosion" conducted by the Kane County bomb squad. The explosion was visible at the southeast corner of the school.
Victims of the "explosion" were carried out on stretchers.
Dozens and dozens of volunteers, playing an unknown role, lined up and got on school buses, which then sat in the parking lot until at least 1 p.m.
People wearing reflective "school incident command" vests could be seen guiding the volunteers.