Hey there! If you have command line access, either as root or as your cPanel user, you could use the "rm" command to remove those files. If they are a very large number of these files (several thousand) you may need to use a more advanced command to take care of that.
One thing I don't like to do is post commands that will delete data on the forums, but I would research the "rm" command and see if that takes care of things for you.