The US Department of Housing and Urban Development, which just filed housing discrimination charges against Facebook for its advertising policies, is reportedly scrutinizing Google and Twitter’s policies as well. The Washington Post writes that HUD officials told Twitter and Google about a probe into their advertising policies last year; a review is supposedly still ongoing. “They want to make sure that other companies aren’t getting away with something that one company is investigated for,” an anonymous source told the Post.

The HUD first announced a complaint against Facebook last year, and it filed the suit soon after Facebook reached a major settlement with civil rights groups earlier this month. While Facebook agreed to remove categories that could allow ad buyers to discriminate against people buying or renting homes, the lawsuit suggested that automated ad targeting in general might present a problem, since it could unintentionally replicate discriminatory categories. That could potentially have implications for all web platforms that run on targeted advertising.

The American Civil Liberties Union, which was one of the groups that settled with Facebook, urged HUD earlier today to expand its investigations. “The HUD complaint is certain to add much-needed pressure on Facebook to eradicate discrimination from its ad platform altogether, and we encourage the department to investigate the wide swath of online ad targeting platforms,” said senior staff attorney Galen Sherwin in a statement.

A Google spokesperson told The Verge that “we’ve had policies in place for many years that prohibit targeting ads on the basis of sensitive categories like race, ethnicity, religious beliefs, disability status, negative financial standing, etc. Our policies are designed to protect users and ensure that advertisers are using our platforms in a responsible manner.” A spokesperson from Twitter said that targeted advertising based on racial or ethnic origin, religion, negative financial condition, or commission of crimes “is prohibited on Twitter under the following categories and we enforce our policies rigorously.”