Investigators were combing through video from school security cameras trying to detect the person responsible, Capt. Greg Graff of the Douglasville Police said.
"What we're leaning toward is it's going to be a prank," he told the Atlanta Journal-Constitution.
About 100 students were hit by the spray in a hallway at Douglas County High School with many complaining of running noses and itching eyes. EMTs were dispatched to the school to evaluate and treat them.
While the area of the school where the spray was released was cleared, the rest of the school was not locked down.
The school is in Douglasville, about 20 miles west of Atlanta.