You can try an locate some of the main cracks and crevices they may be etting in but sometimes figuring out where they got in is impossible. For example we had one get into the radio in the cab of our 4wd tractor. Cralwed in there and chewed on some wires shorting it out. How the heck does a mouse get 15 feet off of the ground and then into the cab radio somehow? I would put out more poison packages under the deck and get a cat. [8D]