SAN FRANCISCO (CBS SF) – Police were investigating a bomb threat at Lowell High School on Monday that forced the evacuation of students.

According to police the threat came around 1:10 p.m., after most students had left campus.

District officials issued a tweet saying police evacuated Lowell High and neighboring Lakeshore Elementary as a precaution.

Lowell students were evacuated to the football field and then released for the remainder of the day.

After a search of the campus, police declared the school to be “safe and clear” shortly before 4 p.m.