Simon Cowell Calls In Security for X Factor Girls

According to our sources, Simon has grown concerned about the safety of the three girls -- Drew Ryniewicz, Melanie Amaro, and Rachel Crow -- after a recent trip to the mall turned into a mob scene.

Our sources says the incident prompted Simon to instruct his personal bodyguards ... they are not to let the girls leave the studio without some form of security. We're told Simon wants the girls to be able to feel safe while doing the kinds of things normal girls do.