It would be difficult to tell without visiting your location. However, we can give you some tips on how to evaluate your control method.

Effective prevention and control of house mouse damage involves three aspects: rodent-proof construction, sanitation, and population reduction by means of traps and/or toxicants. Failure to employ all three portions of the control triad will result in failure and reinvasion.

If your home is truly mouse proofed (which is easier said than done) and you have removed all harborage (places for mice to live), bird feeders, and other food sources (there can be many), then the other problem is often that people fail to use enough traps. Think dozens of traps for a thousand square foot home. Use more if your building is larger.

Try different baits as well; peanut butter or peanut butter mixed with rolled oats is an excellent bait. Don't use cheese. Some mice (and rats) can learn to remove bait without tripping traps. If you're using regular snap traps and your bait is consistently missing, yet the trap is not tripped, consider a trick: hot glue a nut on the far end of the pan (raw almonds work best). Then apply a small dab of peanut butter (pea-sized will do) to the nut. Mice (and rats) cannot seem to pass up a delicacy like a nut. If the nut is firmly attached, the trap will trip.

Don’t forget the attic, crawl spaces, garage, garden shed, and other out-of-the-way areas to set traps. Be sure to properly place your traps.

Visit this site for particulars on trap placement:
Trap Placement

Be sure to wear appropriate protective equipment before entering enclosed places. Safety equipment would include HEPA filter mask and leather gloves. Before using a HEPA filter mask, you should receive training and fitting.

For more information visit
House Mice
House mice guide