Los Altos High School was on lockdown at about 8:30 a.m. after a student reported he heard someone say "it's loaded" in a campus bathroom.
L.A. County sheriff's deputies and police from the Hacienda-La Puente Unified School District converged on the large campus. They searched but found no evidence of a person with a gun.
The lockdown ended at about 3 p.m.