Spanish police said Sunday they have busted a human trafficking ring that brought women from Bulgaria to Spain where they were forced to work as prostitutes and drug their clients to rob them.

Police detained 12 people, 11 Bulgarians and a Spaniard, including the ringleaders, on the Spanish holiday island of Majorca following an eight-month investigation, a statement said.

The gang is suspected of recruiting struggling women in Bulgaria with the promise of jobs and then forcing them to work as street prostitutes or in brothels once they arrived in Spain.

Police said the women were pushed to provide alcohol and drugs to their clients to sedate them and then drain their bank accounts.

"Once they consumed alcohol and drugs, the women would take advantage of the situation by making charges to their credit cards, sometimes exceeding $20,000," the police statement said.

Police said it was difficult to determine how much money they gang was able to steal this way since many of the victims were foreigners who did not file complaints.

Police said they had freed five Bulgarian who were being forced to work as prostitutes in Majorca as part of their investigation, which was carried out in cooperation with their Bulgarian and German counterparts.

During searches carried out at four homes in Majorca police seized more than 10,000 euros worth of cash, several computers, two cars and an undisclosed amount of documents and drugs.