LEWISTON, Maine (AP) Police say a Maine private school teacher has been indicted on 26 sex charges involving a student.

Police say 37-year-old Derek Boyce previously admitted to them that he had a sexual relationship with a 15-year-old female student. The Pine Tree Academy teacher was indicted Tuesday on multiple counts of sexual assault and sexual abuse.

A detective says the victim’s mother came home one night to find Boyce engaged in a sex act with her daughter. She then contacted police.

A spokesperson for Pine Tree Academy says Boyce has been placed on administrative leave and the school believes this is an isolated incident.

It wasn’t immediately known if Boyce has a lawyer, and he did not respond to emails seeking comment.