A southern Illinois high school teacher is jailed on $500,000 bond after being accused of making a bomb threat at her own school.

Illinois State Police say 36-year-old Michelle L. Smith of Jerseyville is charged in Calhoun County with falsely making a terrorist threat.

Authorities accuse Smith of leaving a typed letter in a Calhoun County High School bathroom Monday. Police say the note indicated a bomb had been placed in the Hardin school, which was evacuated. No explosive device was found.