Tenant complaining about rats in the walls.

[Tuan Tran]

I have a triplex where the middle tenant says she keeps on hearing mice or rats running in the walls/ceiling. However, the side tenants do not report hearing anything. I've asked this tenant if she is seeing any droppings or other physical signs. She said no. She did give me a video recording that did have sounds of possibly movement in the walls but I cant say it was conclusive.

Anyone have any experience here and have possible suggestions?