The written note, which threatened to blow up the school, was found in a boys' bathroom around 3:15 p.m. Snyder police searched the entire campus and found no evidence of any explosive device and declared the campus safe.
Police are investigating the incident, including a review of video surveillance from the school.
Snyder ISD officials ask that if anyone has any information about this incident to report it as soon as possible. A reward is being offered.
"Students are reminded that any future incidents could result in an extended school day or Saturday school to make up any time missed and avoid extending the school year into June," said Superintendent Dr. Randy Brown in a statement.