We had a similar experience a couple years after we moved into our house... but with garter snakes.

There was apparently a snake den in the foundation, and they found their way in... not sure what made them do so in mid-Winter. Over the winter, 5-6 of them appeared in our basement. The basement is unheated, so they were very sluggish & easy to catch. We just put them in a 5 gallon plastic bucket on the coldest part of the basement floor, and they hibernated there until Spring, when we released them.
The garter snakes disappeared a couple years later, we figure a skunk or possum cleaned out the nest. We just saw a couple again this year, though - in the garden, where we are happy to see them. A good sign that the area is not completely urbanized yet... hope we can keep it that way. I love any wildlife that does
not eat my garden, doubly so if it kills things that do.