Officials and staff marked completion of retrofit of original Grossmont High School building, now school district headquarters, near the El Cajon-La Mesa border. Photo

Updated 12:40 p.m. Oct. 12, 2017

After scouring the Grossmont High School campus in search of a possible threat to students, police lifted a three-hour lockdown Thursday morning when a threat wasn’t found, district officials said.

“(The El Cajon Police Department) … was unable to substantiate any threat to students, who will have lunch now and resume classes,” Catherine Martin, spokeswoman for the Grossmont Union High School District, tweeted at 11:58 a.m.

Police combed the 66-acre campus and searched about 20 building as they investigated the possible threat for three hours. Canine searches were also done with the assistance from U.S. Customs and Border Protection agents.

The lockdown, with classroom doors locked but instruction continuing, went into effect sometime before 9 a.m., Martin said.

“Students are safe in classrooms,” Martin tweeted at 8:57 a.m.

In subsequent tweets over the next three hours, Martin reported that El Cajon police were investigating a “possible threat” to students but clarified “no students at Grossmont High School were directly threatened.”

In the midst of the search, students were allowed to use restroom facilities in buildings cleared by police, Martin said.

—City News Service