Pet damage from tenant. Please Help!!!

[Alexander Rodriguez]

This is my first rental property, I had it for a bit over a year. Today I got a call from the first floor tenant stating that there is a strong smell like dog/fish in her front porch. She moved the curtain she dad and noticed a stain that smelled very strong. When you see it from outside, now there is a massive stain in the vinyl siding that comes from the second floor, and it smells terrible like pee.

In the second floor there is a tenant that I inherited and has a giant dog. I allowed them to have a dog in their lease of course making them liable for any damages. At this point it’s clear that they allow their dog to pee in their porch.

My concern is that since the damage is inside the wall, if I give them notice to inspect they might try to clean up and cover everything up. So it might be hard to show them liable. (I can’t take pictures of the smell). I was thinking in just showing up and saying that there is a strong odor downstairs and it could be toxic, so I have to go in immediately, then take pictures. Is this legal and reasonable?