MANHATTAN BEACH, Calif. (KABC) -- Manhattan Beach police gave the all-clear to Mira Costa High School Monday after school officials received a threatening voicemail.
The threat was made shortly before 1 p.m.
Students were told to shelter in place in their classrooms with their teachers as police worked to clear the school.
Students were later released to a controlled area for lunch while police continued sweeping remaining areas of the campus, Manhattan Beach Unified School District Superintendent of Schools Mike Matthews said.
Manhattan Beach police said they were aware of the lockdown but did not have details on the specifics of the threat.
Principal Ben Dale said police did not find anything suspicious and declared it safe for students to return to class.
"The impact was to 5th and 6th periods only today, as each of those classes were shortened to 27 minutes," Dale said in an email sent to parents.
It's the third time in the past week the school has been the target of a threat. No further information was immediately available.
All-clear given at Mira Costa High School after threatening voicemail