A reported threat to Mt. Carmel High School in Rancho Peñasquitos Monday was deemed to be unfounded after it prompted a lockdown at the high school and security measures at two others, San Diego police said. “Significant police resources” were sent around 9 a.m. to secure the campus after a call reported a bomb threat at the school. According to police, the threat was deemed unfounded but the source of the threat was still under investigation. Sunset Hills Elementary and Black Mountain Middle School were also placed into a secure campus as a precaution. Secure campus means class instruction continues as normal while campus access is limited. Although the threat was determined not to be credible, San Diego police responded fully to the call. Video from a parent at Mt. Carmel showed several law enforcement vehicles with rifles walking toward campus. A U.S. Marshal vehicle was on site as well as the San Diego Fire-Rescue Department. At least 100 parents flocked to the school waiting for updates from school officials or police. Students were seen exiting classrooms in small groups. By noon, the campus was returning to normal school operations, SDPD said. This is a developing story. Details may change as information is released. ...read more read less