Tenant Occupancy Issues

[Brian Ellis]

Its only been about a month since ive become a landlord, and im already running into an issue with the tenant I took over.

The lease states her and her two granddaughters. I wasn't fond of this considering it is a one bedroom, but I wanted to be as fair as I could. This is what was listed on the rental agreement, so I put it in the lease. 

Since then, I have been over there numerous times working on the other unit. Ive noticed multiple cars being parked, exceeding the limit, and two other occupants there on a daily basis. Totalling 5 people. 

I know it is violating the occupancy square footage laws. If it were a 2 br I would be completely ok with the other two tenants and would have stated it within the lease. But this is clearly a breech in the lease (if they are indeed living there), more than likely they are but I just want to state that this is me and the neighbors assumption. Ive received complaints from one of the neighbors already. This is causing more wear and tear on what the house is made for, and the water bill im sure is going to be through the roof. Like I said, im an understanding person and I want to be able to help them, but this is not acceptable.

What is the best action to take here?