“An unsubstantiated threat” made on a popular anonymous app against an “unknown institution and unknown library” caused El Camino police officers to provide extra security in and around Schauerman Library this afternoon.

“The ECC Police Department received notification today of an unsubstantiated threat against an unknown institution and an unknown library. The threat was via a social media channel, and has since been removed by an unknown source,” according to a Nixle alert sent at 2 p.m.

ECPD Chief Michael Trevis said in an email that no specific institution was named in the threat and other local agencies were notified.

Trevis later confirmed via email the threat was made on Yik Yak, a social media app that has been used to make threats against local area schools in recent months.

In November, Mira Costa High School in Manhattan Beach was closed for two days after a threat was made on the app.

Yik Yak allows users to post questions, comments or threats anonymously. Most posts on the app are about school or relationships. A similar app, BurnBook, was used by teenagers last month who allegedly threatened shootings at Lawndale and Torrance schools.

Minutes after today’s Nixle alert was sent out, a post on Yik Yak time stamped two hours earlier read, “That threat wasn’t funny.” Comments on it included, “What happened,” “Some idiots [sic] gonna get a knock on his door from LAPD. Even if it was ‘just a joke,'” and “So it got reported, right?”

According to the Nixle alert, the Los Angeles County Sheriff’s Department is investigating. Trevis referred questions to Sheriff’s Sgt. Joe Meehan. Multiple calls to Meehan were not returned.