Rialto High School was on lockdown Monday afternoon after a shooting threat was made, according to authorities.
The San Bernardino Police Department, the handling agency, said initial reports came in for a threat of an active shooting around 1:30 p.m.
Officers quickly worked to clear buildings and found no shooter or weapons, police said. The scene was cleared by 2:21 p.m.
According to authorities, one person was detained as a person of interest for the alleged threats. It wasn't clear if any arrests were made.
This is a developing story. Check back for updates.