Authorities now say they're unsure whether a supposed threat to shoot up Los Angeles Valley College was ever made.
About 700 people were evacuated Thursday after sheriff's deputies assigned to the campus got a call from someone who reported overhearing the threat.
Nothing suspicious was found on campus.
Detectives detained a 19-year-old woman at her Panorama City apartment and searched the premises. No weapons were found.
Authorities say the woman denied making the threat and cooperated with investigators. She was released after about three hours without being arrested.
Sheriff's Lt. Rod Armalin says investigators are now trying to determine whether a threat was ever made, and they want to find the anonymous caller who reported it.
Armalin says if the call was phony, the caller could face criminal charges.