The office of Preet Bharara, the United States attorney in Manhattan, has said in court papers that the Flores-Mendez ring was part of a larger network of sex traffickers operating between Tenancingo, Mexico, New York and elsewhere. Women were typically lured through the promise of romantic relationships and a better life, and were forced into prostitution after they arrived, the office said. The judge noted that women who refused to submit were beaten, isolated and starved.

“Because money drives these crimes — as it does so many others — we have pursued forfeiture of the traffickers’ illegal profits and restitution, seeking some recovery for the victims,” Mr. Bharara said in a statement. He added that the victims, mostly poor, without legal status and traumatized and terrorized by the traffickers, were “some of the most vulnerable and powerless in our society.”

Government filings show that brothels were operated at 350 First Street in Newburgh, N.Y.; in a second-floor apartment at 613 Seneca Avenue in Queens; on the second floor of a two-story yellow house at 20 Rose Street in Poughkeepsie; and in an apartment at 121 Elm Street in Yonkers — the busiest of the brothels, with two women working weeklong shifts and each seeing about eight to 10 customers a day.

Prosecutors have estimated that more than 400 women were victims of the trafficking conspiracy, including some who were minors. On one intercepted phone call, a defendant was heard discussing a “new girl who is only 17,” prosecutors said.

Image Prosecutors said women at the Elm Street apartment each saw eight to 10 customers a day. Credit... United States attorney's office for the Southern District of New York

The government said it had been unable to locate or identify the vast majority of the victims, and that of the few who were interviewed by the authorities, most would not cooperate largely out of fear of retaliation. One woman who did cooperate, cited in court records as Victim 1, entered the United States at age 17 with her baby, after the brothers arranged to have her smuggled across the border, prosecutors said.

She was flown from California to New York in September 2006, where the younger Flores-Mendez brother took her to a house on 112th Street in Queens; there she was forced to sleep with her baby under a kitchen table and charged $200 in monthly rent and $50 weekly for food, prosecutors said.