Students at Poway High School were placed on lockdown Wednesday morning following a potential bomb threat, officials said.
Investigators say a note indicating there may be a bomb on campus was found in a girls' restroom, but they could not find out when the note was left.
Administrators did not believe the threat to be credible but treated it seriously, according to a Poway Unified School District spokesperson.
As a precaution, the school was locked down around 9:40 a.m. while San Diego County Sheriff's deputies, Harbor Police and bomb detection K-9s conducted a security sweep of the campus on Espola Road.
There were no injuries. No explosive devices were found.
The lockdown was lifted before 12:30 p.m.
Detectives say they are still investigating who left the note behind. If you know about this case, call the sheriff's department at 858-565-5200 or Crime Stoppers at 888-580-8477.