Dogs......smelly & noisy.

[Jimmy NA]

I just bought a 3 family. Two vacant units. 3rd floor has a young couple. Prior to the purchase I spent time around the property and saw a young guy (not a tenant) going in and out of the property with a small dog. When I finally purchased the prop. I had my first sit down with the tenants. I was introduced by the former owner and went over a few things with the tenants. Again, this young fella was there with the dog. I casually said, "oh, do you live here." " No", he say. I then asked the tenants if the dog was theirs. "No, " they said. Well, Tuesday I sit down with them to sign the new lease. I told them twice no dogs. Well, today I was working in the building and I could clearly hear the dog running up and down the hallway of the apartment and no one was home.

How do I approach this one?