Housing advocates filed a federal lawsuit against Facebook in a Manhattan courtroom this morning, alleging that the social network and advertising platform enables landlords and real estate brokers to exclude families with children, women, and other protected classes from seeing housing ads.

The plaintiffs—the National Fair Housing Association, the Fair Housing Justice Center of New York City, Housing Opportunities Project for Excellence, Inc. in Miami; and the Fair Housing Council of Greater San Antonio—allege that Facebook, by utilizing the personal data of users to help advertisers target (and exclude) specific groups and audiences, enables discriminatory practices that violate the Fair Housing Act.

“Facebook’s platform is the virtual equivalent of posting a for-rent sign that says No Families with Young Kids or No Women, but it does so in an insidious and stealth manner so that people have no clue they have been excluded on the basis of family status or sex,” said FHJC’s Executive Director Fred Freiberg in a statement.

A Facebook spokesperson reached out to Curbed and provided the following statement: “There is absolutely no place for discrimination on Facebook. We believe this lawsuit is without merit, and we will defend ourselves vigorously.”

To prove their point, the plaintiffs created a fake realty firm and prepared dozens of housing advertisements, which they submitted to the social network for review. Facebook provided the fake firm with specific lists of groups that could be excluded from seeing the ads, including families with children, moms with children of certain ages, women or men, and other categories based on sex or family status.

Plaintiffs conducted investigations in each of their housing markets to confirm Facebook’s allegedly discriminatory practices.

The investigations also revealed that Facebook provides housing advertisers with the ability to exclude certain “interest” categories from receiving ads that are disability-based (people who are interested in disabled veterans or disabled parking permits) or national origin-based (people who are interested in English as a second language).

The investigation into Facebook, which has more than two billion active users, comes as the social network continues to deal with the fallout from Cambridge Analytica, and the mishandling of data from 50 million users.

This isn’t the first time that Facebook has been in trouble for potentially discriminatory housing advertisements. An investigation by the news organization ProPublica that began in 2016 found that Facebook’s ad platform permitted advertisers to exclude African Americans, Latinos, and Asian Americans from receiving ads for housing and other goods and services.

ProPublica then followed up on their initial report last November and found “major omissions” and a “significant lapse in the company’s monitoring of the rental market”

Today’s complaint notes that while the company has responded to those earlier findings and removed some ad targeting options, it still continues to violate fair housing laws in other ways.

One of the plaintiffs’ lawyers, Diane L. Houk, told the New York Times that they want the court to order Facebook to “develop a plan to remove any ability for advertisers to access Facebook’s checklists for excluding groups of people in the posting of housing-related ads.”

“Facebook announced this year that its new mission is to bring the world closer together, but this remains empty corporate jargon as long as Facebook discriminates in its ad platform,” said Katherine Rosenfeld, another attorney for the plaintiffs. “If Facebook truly wants to bring the world closer together, it could start tomorrow by giving female-headed families with children equal access to Facebook advertisements for apartment rentals.”