Authorities placed a Turlock school on lockdown Monday morning after receiving an anonymous tip of an armed student.
Stanislaus County Sheriff's deputies and California Highway Patrol officers responded to Roselawn School to do a safety sweep after receiving the tip.
It is unclear if the student left the school on the bus or what type of weapon was seen.
About 40 students already on campus have been secured safely while the sweep takes place.
A bus with students has yet to arrive.
Further details will be posted as they become available.