If it stinks like mouse pee,,, you know who put it there. if not, then the dreaded previous owner AKA DPO,
I live out in the country and we have LOADs of mice and rats, hard to cut off their food sources as theres no lack of seeds and other stuff for them to munch on, Im always getting them in my shop and storage areas, I use a LOT of DECON rat and mouse poisons and ONE BITE, but im very careful as I dont want my dogs or other critters to get poisoned. My other issue is we have a lot of Hawks and eagles that hunt on our property and surrounding fields so while i would like to,,, i cant put out much poison,, dont want to kill any of the eagles.
I once started up a bike that sat all winter,, FWOOM! Out the exhaust pipe came a huge mouse nest and a big cache of stolen dog food. Ive gotten them in the heater boxs in my truck too. that sucks to clean out.