Authorities say the anonymous phone call was made at about 9:10 a.m.
"We received a credible threat that someone was going to be responding to our Los Angeles Valley College campus, and that someone might be involved in perhaps shooting up the campus," said Lt. Melva Mitchell of the L.A.S.D. Community College Bureau.
The Valley Glen campus located at Burbank Boulevard and Fulton Avenue was immediately evacuated, and classes were canceled. Grant High School was also placed on lockdown as a precaution as authorities searched for the suspected shooter.
The woman, identified as a 19-year-old former student, was detained at an apartment building at Sylmar Avenue and Plummer Street in Panorama City at about 11 a.m.
It was earlier reported that the woman was 21 years old. According to the L.A. County Sheriff's Department, the woman is 19 years old.
A SWAT team responded and cleared the building. It was earlier reported the woman was arrested. She was detained, according to the L.A. County Sheriff's Department. She was being questioned for her involvement into the threat. She told investigators she was not the person who made the call and that she was being falsely accused.
"We are detaining her. The investigation is going on. We're trying to determine if there are additional 'folk' involved," said Mitchell.
Investigators were searching for another individual and planned to work overnight.
According to the college, evening classes after 5 p.m. will resume for final exams only.
The incident was handled by deputies with the sheriff's Community College Bureau, which patrols the nine campuses of the Los Angeles Community College District.