"We're aware of the allegations involving a high school teacher and a high school student, and there's an ongoing investigation. That's really all I can say," said District 3 District Attorney Ben Creekmore.
He declined to discuss the allegations.
The Tippah County Sheriff's Department is carrying out the investigation, since the alleged activities are believed to have taken place outside Ripley city limits. Efforts to reach Sheriff Karl Gaillard Tuesday weren't successful.
Sources identified the former teacher as Melissa Mathis.
Superintendent Frank Campbell declined further comment on the resignation.