Acalanes High School in Lafayette is currently on lockdown because of threats posted to social media, officials said.
Police said students are safe, and there is no immediate threat at the high school.
Contra Costa County Sheriff’s Office spokesman Jimmy Lee said the school went on lockdown after school officials became aware of a threat on social media.
Lee said officers are trying to figure out if the threat is legitimate and no arrests have been made.
Police are at the school and are investigating the situation.
UPDATE, 1pm: The following update is from the Lafayette Police Dept.:
Earlier today police received a perceived threat to Acalanes High School. Police secured the school, searched the campus and detained a subject off campus. The subject was not on or near the campus. The School Lockdown has been lifted.