Spanish police say they have freed 11 women, most of them Ukrainian, who traveled to Spain thinking they were taking jobs as hotel chambermaids but were forced to work as prostitutes.

The National Police said in a statement Tuesday they believe the international gang had forced more than 200 women into prostitution in the same way since 2015.

The statement said the women were lured by online advertisements offering a loan to travel and well-paid hotel jobs in Burgos, a city in northern Spain. After arriving, they were forced under threat of violence to work as prostitutes 10 hours a day, seven days a week. Fines ensured the loans were never paid.

Two Spaniards and two Ukrainians were arrested on suspicion of human trafficking and criminal organization, among other crimes.