SAN BERNARDINO, Calif.—A sheriff's deputy who worked in a San Bernardino County jail has been arrested on suspicion of having sex with a female inmate.

Deputy Johnathan Miller was released from jail Thursday after posting $25,000 bail.

The Sheriff's Department said in a news release that the staff at Glen Helen Rehabilitation Center information that the 27-year-old Miller was having inappropriate but consensual contact with the 25-year-old inmate, whose name has not been released.

An internal investigation was launched Tuesday, and Miller was arrested Wednesday.

The sheriff's statement says Miller violated a law forbidding jail and prison employees from engaging in consensual sex with inmates.

It is not clear if Miller has hired an attorney, and a phone number listed under his name was disconnected.