LITTLETON, Colo. — Columbine High School was on a lockout Monday after a bomb threat was made to the school, KUSA-TV reported.

The threatening call reportedly came in around 12:30pm local time (2:30pm ET) and officials have since barred anyone from entering the school building in Littleton, Colo.

Jefferson County deputies were on the scene investigating, KUSA said.

The threat comes just days before the 13th anniversary of an infamous shooting spree at Columbine High School, in which two teenagers shot and killed 12 of their classmates and one teacher.