Scoop the mice up and if you don't want to breed mice anymore find a pet store that will take them.

If you don't have a use for the mice find a good alternative for them.

And regarding them "being out all night" what if your BP got out all night? Would that immediately imply he was full of vermin and poisons and is now a health risk? Of course not. I wouldn't be feeding any mice that were out all night to your snakes right away, but sheesh, they probably didn't get into anything.