Students at the Enid High School were evacuated on Monday after a cylinder with wires and a threatening note was discovered inside a bathroom at the school.
According to school officials, the object was later identified as an air-conditioning capacitor. Law enforcement officials determined there was no danger.
Students were evacuated to D. Bruce Selby Stadium and parents were told they could pick up their kids early.
"Safety is our number one priority," said Amber Graham Fitzgerald, Director of Communications at the school. "While it is rare that a situation occurs, we coordinate regularly with local law enforcement so that we can be prepared when necessary. We appreciate their assistance."
An investigation is now underway.