PITTSBURGH — A third teacher at Plum High School has been accused of having sex with a student.

Allegheny County District Attorney Stephen Zappala Jr. on Tuesday announced the arrest of Michael Cinefra, 29, of Verona, a former a substitute teacher at the high school.

Prosecutors allege that he played a cell phone game with a 15-year-old girl and exchanged texts with her, then bought her alcohol and engaged in sexual contact.

Zappala said the arrest was unrelated to the other two cases involving teachers at the school. Joseph Ruggieri, 40, and Jason Cooper, 38, were earlier charged with institutional sex assault and with witness intimidation. Witness intimidation charges were also filed against teacher Drew Zoldak, 40.