(Associated Press) Hundreds of women were brought from Thailand to the U.S. and forced to be “modern day sex slaves,” according to an indictment unsealed Thursday that charges high-level members of what authorities called a sophisticated sex-trafficking ring that concealed millions of dollars in earnings.

The indictment brings the total number of people charged to 38, making it one of the largest sex-trafficking prosecutions in the U.S., said Acting U.S. Attorney Gregory Brooker. Authorities say the operation lured Thai women to the U.S. with promises of a better life, then forced them to work as prostitutes until they could pay off often insurmountable bondage debts.

Women were rotated through several prostitution houses around the U.S., forced to work long hours, and “forced to have sex with strangers, even if the men were abusive,” Brooker said.

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