Two Taylor County High School teachers are accused of having sexual relations with students, says Robert Devane, an investigator in the GBI's Midland office.
He said one of them is the school's band director, 53-year-old David Van Buren.
Devane said Van Buren was charged this spring after two girls came forward. He's facing two counts of sexual assault on a person in custody.
After his arrest, Devane said, a student on Facebook commented, "They got the band man. Mr. Walker is next."
Devane said that led them to another suspect: 42-year-old Shannon Walker. He was a ninth-grade History and Social Studies teacher.
He said Walker currently faces only the charge of interfering with custody, but may face further charges next week.
The case was also turned over to the FBI, he said, because Walker allegedly took an underage girl across state lines.
Taylor School Supt. Wayne Smith said Walker resigned last week after he brought the resignation letter to jail and Walker signed.
Smith says he plans to schedule a termination hearing for Van Buren. He says he asked the band director to resign, but he would not.
Smith called the incidents "very unfortunate" and said they have "no place" in Taylor County schools.