If the steps have 'gaps' between them and, say, the walkway or driveway where they're gaining access, first - get your garden hose and clean out the gaps. Second - Buy some Concrete Caulk (and a caulking gun) from you local Home Center, and seal them babies up!!!
If we're not dealing with gaps but, instead, dealing with a large, open area in which they're gaining access under the steps, you can do as Steve: suggests. Also, sometimes, if you 'open up' the area by pruning bushes and such, in order to improve airflow, sometimes, a change in the 'environmental conditions' will force them out of there. I wouldn't go drowining them because they probably like the damp, moist conditions. Get some sun and air into that area, and maybe they'll go away because of the change.
There are these 'ground plugs' that you can use to capture them but I'm not a big fan of them. IN a way, you're ATTRACTING them to get rid of them. Maybe turing the soil every day will evict them.