Ontario police said officers arrived to the mall around 1:45 p.m. after reports of a disturbance and were investigating if a crime happened.
They determined a group of people ran through the mall, causing panic among shoppers.
"Ontario Dispatch then received multiple calls claiming a person had a gun and gun shots were heard. It has been determined that there was no gun or shots fired," Ontario police tweeted.
The police department said it will investigate the false claims and hold any suspects accountable.
Police said the mall remains open and is safe.