SANTA CLARITA, Calif. (AP) — Authorities are investigating online threats against schools near the Los Angeles-area high school where a 16-year-old boy shot and killed two classmates and wounded three others.

Sheriff’s officials said Sunday that investigators have not found any of the threats made on social media to be credible.

Meanwhile detectives are searching for a motive for the killings carried out Thursday by Nathaniel Berhow at Saugus High School in Santa Clarita. The teen shot himself and later died. Authorities say Berhow didn’t appear to be linked to any ideology.

A wounded 14-year-old girl was released from the hospital Friday. A 15-year-old girl remains hospitalized in good condition.

Officials didn’t say how many recent threats are being investigated. Additional law enforcement will be posted at schools Monday.