Mice like to chew on wires such as in the attic which could start a fire. Call around and tell companies that you want humane removal. Don't delay.

I don't like the poisons that pest control leaves around to kill the pests.
Get a "tin cat"....a catch and release ( if you want to ) mouse trap. I can do with a lot of mice problems before I can deal with baits and spray poisons around my house.
And get some steel wool and stuff it into every tiny crack in your house.

I had good luck with putting in several sonic mouse repellents.

Immediately. If you are unwilling to use good ole snap traps, you can find a pest control company that traps and removes then humanely,though I wouldn't recommend it. Mice are filthy and destructive, not to mention an excellent attractant for snakes. That's right. Snakes. In. The. House. Not good. Mice are no use alive. Period.

I have heard that peppermint oil repels them, but that myth has been debunked,as I found a colony of them living in the ground directly beneath a huge patch of peppermint in my yard. They were frolicking through the frickin mint. I tried to let it go,as they were not in the house. Until one day, I went to change my dogs water. I turned the cooler over to empty the water out. I washed out the cooler, turned around, and coiled up in the spot where the cooler was was a huge,grumpy,and well fed rattlesnake. After dispatching the offending serpent, SO got some gas and poured it down the mouse holes. The fumes got rid of them. I wouldn't recommend you do that in your house though. :) But I digress. A good pest control company will also look for any entrances they are using to get in your house and seal them. I would have called them the first time I saw one or any of the "evidence" they tend to leave all over. For every mouse you actually lay eyes on, there are probably a dozen more skulking around,spreading disease.Good luck.

It is possible there is just one mouse, this happened to me in my last house. They can come in unbelievably small spaces. I tried every kind of trap I could find and in the end the glue traps were the only thing that caught it. Disgusting I know but as others have said a mouse can wreak havoc on your home particularly electrical wiring so the sooner you get rid of the problem the better.

Okay, the snake stuff might make me be a little more aggressive in getting rid of these guys. Time to call the exterminator. Gross!

Charmain I don't know where you live, but the only time I have heard of snakes living in a house has been in the south, where there are a lot of snakes and they are looking for a cool place to hide. Unless your house is a LOT more mouse infested than I think, there is always more food for the snake outside than inside your house. If snakes are living in your house, they are seeking shelter and not food.
Call the exterminator if you wish, but be prepared for baits and poisons and for keeping a very close watch on your kids and pets.
I am not averse to a clean killing snap trap of two, and a few de-con pellets hidden carefully

Why would you simply kill a snake you found outside. Snakes control a lot of pests. I'm actually "afraid" of snakes, but when we discover them in our yard we let them be.

Also, why would anyone kill mice living outside in tunnels unless they were relocating inside your home.

There is never only one mouse...