Facebook’s business model is under scrutiny again for its alleged role in perpetuating job discrimination.

A group of women Facebook users filed a gender discrimination complaint with the US Equal Employment Opportunity Commission on Tuesday, accusing the social media giant and nine other companies of posting biased job ads on the platform, according to the New York Times.

The businesses reportedly bought ads on Facebook to publicize job openings, but targeted them so that no women who use the platform could see them. The jobs included positions for truck drivers and window installers, according to the report.

The women claim that hiding employment ads from an entire gender of job seekers is a violation of the Civil Rights Act, which makes it illegal for employers to discriminate against workers and job candidates based on gender, race, and other protected traits. The EEOC complaint was filed with support from lawyers at the American Civil Liberties Union and the Communications Workers of America, though it’s unclear how many women they are representing.

A spokesperson for Facebook, in a statement to the Times, said the company’s policies strictly forbid discrimination. “We look forward to defending our practices once we have an opportunity to review the complaint,” the statement said.

The complaint renews focus on one of the key legal challenges for Facebook’s unique business model, which lets advertisers micro-target the network’s users based on their interests, city, age, and other demographic information.

While it’s generally not against the law for businesses to advertise services to people of a certain race or age, it can be illegal in certain contexts. For example, ad campaigns related to housing, real estate, financial services and job opportunities cannot exclude black and Latino consumers.

In recent years, civil rights advocates have sued Facebook for accepting ads that discriminate against consumers based on their religion, race, and gender. The tech company is also accused of age discrimination in a class-action lawsuit filed in May by older Facebook users who were looking for jobs.

Facebook has argued that the company is not legally responsible when other companies buy ads that violate the law. Its lawyers have cited the Communications Decency Act, a federal law that protects internet companies from liability for content created by third parties. But user groups argue that Facebook ads are not third-party content because the company developed the micro-targeting ad technology.

In the complaint filed Tuesday, lawyers showed how the company’s ad-building tool let businesses exclude women from seeing job posts. A Facebook disclosure for a job ad posted earlier this year by a furniture store in Texas said the business was trying to reach men between 18 and 50 years old near the city of Fort Worth, according to the Times.

Lawyers collected similar job ads posted on Facebook between October 2017 and August 2018, and they filed the complaint on behalf of all women Facebook users who were looking for jobs at the time.

Under federal law, workers and job seekers must first file discrimination complaints with the EEOC before they can sue in federal court.