SAN RAMON, Calif. (KRON) — California High School in San Ramon was placed under lockdown on Wednesday due to a violent threat, according to an alert sent out by the local school district. The lockdown was since lifted.

San Ramon Police Department officers and drones searched the campus and found nothing suspicious, SRPD said. Police remained on campus and in surrounding areas to investigate.

During the lockdown, the campus, located at 9870 Broadmoor Drive, was locked, the lights were out, and students and staff members were out of sight. Visitors and parents were not allowed on campus while it is locked down.

Students will be released with a regular protocol, and afterschool activities will resume as normal, the school district said. TRAFFIX buses will arrive to pick up students.