They may have found food or shelter. Make sure you block any places they may be using for shelter. Also, don't put food out for them and make sure they aren't getting into your garbage. If the cats belong to your neighbors, they will eventually wonder back home.
If you think they are strays, you may want to call a no-kill shelter to come get them. Or you can set live-traps and bring them into a shelter.
Best of luck!