Police believe many women are brought to England illegally
An operation into the trafficking of sex workers has been revealed by BBC Inside Out which followed police officers during the year-long investigation.
Norfolk Police believe there could be up to six Chinese and Thai brothels in Norwich alone, which use trafficked women.
Using information from raids, officers tracked down and prosecuted the mastermind behind at least three brothels in Norwich and Ipswich.
But this prosecution is just the start, and they now intend to pursue those they believe are higher up the chain of exploitation.
Detectives believe many of the women working in the brothels in Ipswich and Norwich have been brought into England illegally.
These women are forced to work as prostitutes to pay off tens of thousands of pounds to those who have brought them here.
When Mai Ling (not her real name) was growing up in Thailand, she dreamed of becoming a vet.
Instead she ended up working in a brothel in Norwich to pay off family debts.
"I felt shocked when someone offered me to do this job, really shocked.
"But by that time my father was in hospital, I got to look after him. I've got no choice," says Mai Ling.
She was eventually rescued by Norfolk Police and officers hope to save other women from a similar fate.
They followed the trail of Yi Yuan Geng, believed to be the mastermind behind several Chinese prostitution operations in Norwich and Ipswich.
During the year-long operation they raided addresses in Norwich and Ipswich suspected of being brothels run by Geng, but Geng herself proved elusive.
After many months of work, using evidence discovered during the raids, they tracked her down in London.
Yi Yuan Geng was charged and found guilty of managing two brothels in Norwich and one in Ipswich. She was sentenced to 18 months in prison followed by deportation.
Det Sgt Stuart Bailey, who headed the operation, said: "The result wasn't just for us, it was for all those she exploited."
The Inside Out programme will be broadcast on BBC1 at 1930 GMT on Monday 7 December.
Inside Out accompanied police on a raid