Switzerland of Ohio School Superintendent Larry Elliott said River High School was on lockdown for part of the morning due to a safety issue.
Elliott said the safety concern was investigated and classes have resumed again.
The Sheriff's Department was called to the High School but following an investigation classes resumed again.
Elliot said students and staff are all safe and things are back to normal.
The superintendent did not want to disclose what the safety concern was until he received a full report on the issue.