SAN FRANCISCO (KCBS)— Lowell High School was evacuated for almost two hours on Tuesday according to the San Francisco Police Department. School officials said a bomb threat was called in at 1:15 p.m. before police arrived five minutes later.

SFPD spokesman Gordon Shyy told KCBS that the school’s principal contacted the police department to report that the school, located at 1101 Eucalyptus Dr., had received the threat.

Police initially declined to say what the nature of the threat was, but confirmed that all students were taken safely to the sports field while a sweep of the campus was conducted.

Police gave the all clear just before 3 p.m.