North Wales Police, which covers the Chirk area, has posted a warning on its Facebook page to alert about women from Eastern Europe, Thailand, and Nigeria who are forced into sex.
It is potentially tied to modern slavery and sexual exploitation, they warn.
A police spokesman said: "Modern slavery and sexual exploitation can happen in 'pop-up brothels'.
"These are usually newly acquired properties, privately rented flats or houses, in towns and cities, budget hotels or holiday properties which may only be used as a brothel for a short period of time.
"Many of the women forced to work in these brothels are Eastern European, Thai, and Nigerian; and may also be living in the property for the short period of time the brothel is running."
Police say these are some of the signs to look out for:
Less activity than you would expect when new people move into a property (for example, no removals)
Limited furnishings – the property doesn’t appear lived in
Multiple women living at the address, or who may be brought in and out of the address by an individual
Multiple vehicles visiting the property at a time
Many frequent visitors, usually male, who don’t stay for long periods of time
Police ask that if you think a pop-up brothel may be operating near you, you can report anonymously to Crimestoppers on 0800 555 111 or complete a form online at orlo.uk/T07pJ.
You can also contact police on 101 or report online at orlo.uk/SEyUu.