Metro is pulling ads for a new book by controversial alt-right writer Milo Yiannopoulos after riders raised concerns about the promotional posters that began appearing throughout the transit system last week.

“The ad violates Metro’s advertising guidelines. We are in the process of removing the ads,” Metro spokesman Richard Jordan said in a statement Friday.

Jordan did not comment on how many of the ads appeared in Metro stations, or what prompted officials to take a closer look at whether the posters comported with Metro’s policies. (Metro uses a third-party contractor, Outfront Media, to solicit and design advertisements for the system; not all ads are reviewed by Metro officials before they are posted inside stations and on trains and buses.)

Regardless of whether Metro initially realized the controversy looming behind the promotional posters, it became clear in recent days over social media that many riders were not pleased to see Yiannopoulos’s visage inside their stations.

Yiannopoulos became an increasingly public — and polarizing — figure in recent years as a columnist at the alt-right media outlet Breitbart. He espoused ideas that were widely seen as racist, xenophobic and sexist — and made an even bigger name for himself when he was banned from Twitter for harassing  actress Leslie Jones, who is black.

But it wasn’t until last February that Yiannopoulos started to pay big for his controversial views. After footage surfaced of him that suggested that he supported pedophilia, he was forced to resign from Breitbart and his multimillion-dollar book deal was dropped.

He later chose to self-publish his book, “Dangerous.” It has already reached the top of the book-sale charts on Amazon.

Asked why the book ad was inappropriate for Metro stations, Jordan pointed to two bullet points in the advertising policy: a ban on “advertisements that are intended to influence public policy” and on “advertisements intended to influence members of the public regarding an issue on which there are varying opinions.”

In the past, Metro’s decisions to ban controversial advertisements from subway stations have often resulted in lawsuits, with some critics arguing that the transit agency’s guidelines are excessively broad or unfairly applied.

Earlier Friday, Yiannopoulos filed a $10 million “breach of contract” lawsuit against publisher Simon & Schuster for terminating his book deal.