Three Chicago-area brothels have been shuttered and the people who allegedly ran them have been arrested after an 11-month investigation by Cook County sheriff’s investigators and federal agents, authorities said Wednesday.

On Tuesday, investigators with Sheriff Tom Dart’s vice unit and U.S. Homeland Security Investigations raided apartments they believe were operating as brothels. Two of the apartments are in Chicago in the 3900 block of West Lawrence and the 4500 block of South Archer. The third apartment is in the 10000 block of Holly Lane in unincorporated Maine Township.

Three people have been charged in Cook County Criminal Court with promoting prostitution, including Antonio Cruz, 46, of Chicago; Maria Lopez, 49, of Glenview; and Salomon Diaz, 19, of Aurora, according to the sheriff’s office.

Three suspected customers also were arrested, authorities said. Six women working in the brothels have been provided with housing and access to social services and counseling.

Authorities said the brothels had attracted a large number of “johns,” with one apartment servicing at least four customers per hour, officials said.

The investigation began with a tip to HSI that foreign nationals and others were involved in prostitution in the Chicago area, a spokesman for the agency said.

In addition to the prostitution-related arrests, there were “various immigration arrests” that occurred as a result of the investigation “or involving individuals who were arrested at the various scenes of yesterday’s activity,” the HSI spokesman said.

He declined to comment further on the immigration arrests “until such time as the criminal case proceeds.”

Last month, a separate investigation by the sheriff’s office and HSI resulted in federal charges against six Chicago-area people accused of participating in an international prostitution ring involving Thai women.

A spokesman for the sheriff’s office said the alleged brothels that were raided Tuesday aren’t suspected of being involved in international human trafficking as the Thai ring was.