Detectives have been interviewing 19 women they believe were tricked into working as sex slaves in a Birmingham massage parlour.
The women, aged between 19 and 30, were rescued from Cuddles on Hagley Road on Thursday evening by a special task force of about 25 female officers.
Two men and a woman, from the West Midlands, were arrested.
Twelve of the women are expected to be released but seven will be held pending checks on their immigration status.
The women are said to come from Greece, Hong Kong, Italy, Japan, Latvia, Poland and Turkey.
It is thought some of the women might have been deported from the UK previously, but were then brought back by human traffickers.
A shotgun and £7,000 were found at the premises which police say was being used as a brothel.
A West Midlands Police spokesman said: "The women are believed to be of Eastern European origin and were tricked into the sex industry.
"They had their passports taken. They were locked into the venue during the evening to work and taken away during the day and locked in a house."
Det Insp Mark Nevitt said they believed the women came from about 10 countries.
"We now need to... speak to them, debrief them and find out exactly how they got into the country and what their role is within this establishment," he said.
Ana Fonseca, from International Organisation for Migration, which works to help women in such situations, said there were many other women around Britain in the same predicament.
Deporting the women was not the answer and it needed measures to tackle poverty and offer training.
"It is important that you offer training, that you can help them find employment, so that they can sustain their families so they don't have to become vulnerable again," she said.
Amnesty International welcomed the raids but has called on the UK Government to do more to protect victims of trafficking.
Amnesty spokeswoman Sarah Green said there was no protection in law for victims of trafficking, who are usually classed as illegal immigrants and deported.