Twenty brothels posing as legitimate businesses from Rhode Island to North Carolina were shut down and 31 people were arrested, allowing more than 70 sex workers enslaved by a human trafficking ring to be freed, officials said Wednesday.

The arrests capped a 15-month probe that began when a Korean couple who owned and operated a chain of brothels in Queens tried to bribe an undercover New York Police Department detective, said Julie L. Myers, assistant secretary for U.S. Immigration and Customs Enforcement.

Myers said it was disheartening to hear agents describe stories "of women who were promised a better life and instead held as sex slaves" at brothels posing as massage parlors, health spas and acupuncture clinics in New York, Washington D.C., Connecticut, Pennsylvania, North Carolina, Maryland and Rhode Island.

U.S. Attorney Michael Garcia said the smuggling organization relied on recruiters who went to Korea and found young women eager to live in the United States.

The recruiters charged the women tens of thousands of dollars to provide false documentation to enter the country or to smuggle them in, he said. Once in the United States, the women were placed in brothels, unable to leave the business until their debt was paid, he said.

Identity and travel documents were seized from the women, and they were told their family members would be harmed or they would be turned over to authorities if they tried to leave, Garcia said.

Myers said the Flushing, Queens, couple who touched off the probe paid at least $125,000 to the undercover detective. The couple was arrested in March along with two police officers who were discovered during the investigation to be accepting bribes to keep quiet about the brothels, authorities said.

Those arrested Tuesday face federal charges including conspiracy to engage in human trafficking, prostitution and conspiracy to transport illegal aliens included brothel owners and managers, middlemen who worked as transporters and individuals who handled the money. If convicted, the suspects face maximum sentences of five to 10 years.