A teacher at Heard County High School has been charged with having an inappropriate relationship with an 18-year-old female student, authorities said Thursday.

Thomas Sickman has been charged with sexual assault by a person with supervisory or disciplinary authority, according to a media release from the Heard County Sheriff’s Office. The teacher turned himself in and has been jailed without bond, pending a hearing.

The charge comes after an investigation by Franklin police, the Heard County Sheriff’s Office, and the Georgia Bureau of Investigation. The investigation began Friday, when Heard County School Superintendent Jerry Prince contacted Franklin Police Chief Kevin Hannah over the allegations.

Evidence and statements gathered during the investigation sustained the allegations, and an arrest warrant was issued Thursday for Sickman.

Sickman is listed as an American government and civics teacher on the Heard County High School website. There was no word on his job status.