Cal High School in San Ramon lockdown lifted after initial threatening phone call, police say

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

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.

As of 12:38 p.m., police said that the school had been thoroughly searched and cleared.

"The lockdown of the campus has been lifted, but it is remaining in a 'secure' campus mode, which means students will be allowed to move throughout the interior of the campus, but outside individuals will be kept off campus. Out of an abundance of caution, San Ramon Police personnel will remain on campus throughout the remainder of the school day to ensure the utmost safety of those on campus," police said in a statement.

The incident reportedly began Thursday morning when front office staff received a call from an unidentified man. During the call, he reportedly stated that explosive devices had been placed throughout the school. He also said someone would be arriving shortly to shoot up the school, according to authorities.

"Based on the specific language and details mentioned by the caller, the decision was made to conduct an extensive search of the campus using explosive detective K9s, who were escorted throughout the campus by uniformed officers," police said in a statement.

Immediately after the call, the school was placed on lockdown.

Detectives are investigating the origins of the call in an attempt to identify the caller.

No additional information was provided.

This is a breaking news story. Check back for updates.