California High in San Ramon receives threatening call

California High School in San Ramon was placed on lockdown Thursday morning following a threatening phone call to staff, according to police. 

During the phone call, a man said that  explosive devices had been placed throughout the school and that someone would be arriving shortly to shoot up the school, police said in a statement.  

At about 10 a.m., San Ramon police announced that they were providing extra security to the school and that the campus was locked down after someone phoned in a threat of violence. 

Police said they sent in explosive detection K-9s and uniformed officers began escorting students and staff to the front office.

Police were also searching the parking lots and sports fields and warned the lockdown could take a while.

Meanwhile, detectives said they were trying to figure out the origin of the call.