Fix and flippers used poison for mouse problem, dead mice in the ceiling

Pretty much like the title says. It's become evident that there was a mouse problem in the house. We haven't seen any evidence of recent activity, but I know it's possible there are still mice around anyways. One of the bathroom started leaking (of course ), and we had to open up a section of the ceiling in the basement. Inside there are at least 6 dead mice in two square feet. We found evidence of the fix and flippers using deodorizers in the house, after closing, and now we know why. I believe they used poison to kill the mice and they died inside the walls. Fix and flipped houses really are a nightmare.

What do we do? Seal it up and pretend we saw nothing? Rip every wall out of the house? Insurance nor home warranty covers pests...