A Gwinnett County sheriff's deputy was in jail without bond Thursday after allegedly having sex with an inmate.

Deputy Duone Clark was arrested on Wednesday and charged with sexual assault and violation of oath by a public officer, according to Gwinnett sheriff's Lt. Sean Smith.

Smith said that an internal investigation was launched into allegations that Clark "engaged in sexual activity with an inmate while in custody at the jail,"  and Clark was placed on administrative leave.

"Authorities secured enough evidence, along with witness statements, to secure warrants for Clark's arrest," Smith said, adding that Clark has since resigned from the department.

Smith said that Clark, 40, of Lilburn will be housed at another facility "for safety and security reasons."