@Alfred493 Does the number of people there exceed your legal limit? Message the guests and tell them anyone not on the original booking has to leave immediately, as they are trespassing and their presence invalidates your insurance and contravenes the terms of their booking.
If you have an extra guest fee, by all means, ask them to pay. But if I were you, I would just make sure the other people leave. If they won't, call the police- they are trespassing.