The complaint identified nearly a dozen businesses in Manhattan that it said had operated as brothels, including Asian Flower at 599 Avenue of the Americas, near 17th Street; Secret Diary at 156 East 33rd Street, near Third Avenue; and Rainbow Spa at 45 East 34th Street, near Madison Avenue. It was unclear if the businesses were shuttered as a result of the investigation.

Some of the brothels posed as legitimate enterprises, like a spa, and kept lists of patrons who had been “vetted or vouched for by other brothels or customers” and would cater only to them, the complaint said.

Often the brothels identified by investigators specialized in a form of prostitution referred to as a “Girlfriend Experience,” or G.F.E., which was often priced at double the usual rate, the complaint said.

The women would sometimes be rotated among a group of brothels with established relationships, “in order to offer ‘new girls’ periodically,” the complaint said. Some clients would “email the brothel specifically to ask if any new or different girls are available.”

The complaint made it clear that investigators had assistance from two cooperating sources. One cooperator worked in various brothels as a manager, making appointments for customers, collecting money and paying advertisers; the other, a Korean woman who came to the United States in 2003, worked her way up from being a prostitute to running a brothel.