Around 2:50 p.m. officers were dispatched to Pinole Valley High School at 2900 Pinole Valley Road after an anonymous caller told school officials that students were to be shot when they were let out of school.
The school's principal locked down the school as a precaution until the area could be deemed safe, police said. Parents of students were contacted of the situation through a calling tree.
The area around the school was searched by officers with the Pinole Police Department, the Hercules Police Department, the Richmond Police Department, the Contra Costa County Sheriff's Office and the California Highway Patrol. A sheriff's office helicopter also searched the area, including the school's rooftops.
Once the area was secure students and school staff were released from the school and there were no reported injuries.
Anyone with information about the threats can call police Detective Justin Rogers at (510) 724-8958.