Joe Tidy of BBC News reported that the BBC was able to use keyword targeting to serve ads on Twitter to people who showed interest in keywords related to hate groups or discriminatory terms, and the ads were approved and went live on Twitter.

A Twitter spokesperson told Tidy policies are in place to avoid keyword targeting abuse, but they were not applied properly.

The social network said in a statement, “Our preventative measures include banning certain sensitive or discriminatory terms, which we update on a continuous basis. In this instance, some of these terms were permitted for targeting purposes. This was an error. We’re very sorry this happened and, as soon as we were made aware of the issue, we rectified it. We continue to enforce our ads policies, including restricting the promotion of content in a wide range of areas, including inappropriate content targeting minors.”

According to Tidy, the BBC created an ad from an anonymous Twitter account, simply saying, “Happy New Year.” It then chose three different U.K. audiences to target, based on potentially sensitive keywords.

The ad moved to a pending state during Twitter’s review stage, and it was subsequently approved and live on the platform for a few hours before being removed by the BBC.

Tidy reported that 37 Twitter users saw the post and two clicked on a link that was included, which directed them to a news article about memes. The ad cost £3.84 ($5.02) to run.

The BBC also shared data on the potential audience that could be reached via those keywords.

For comparison’s sake, Tidy said the potential audience for an automotive website seeking to use the term petrolhead—meaning a person who is overly reliant on his or her car—was estimated by Twitter at between 140,000 and 172,000 in the U.K.

The BBC found that targeting via the term neo-Nazi generated a potential audience of 67,000 to 81,000, and those figures rose to 92,900 to 114,000 for a campaign using the keywords Islamophobes, Islamaphobia, Islamophobic and #islamophobic.

Potentially vulnerable groups were at risk, as well, as the BBC ran the same ad in the test described above, targeted to people between the ages of 13 and 24 via the keywords anorexia, anorexic, bulimia and bulimic.

The estimated audience was 20,000, and the ad was seen by 255 users and clicked on by 14 of them before being pulled by the BBC.

The ability to target Facebook users with ads based on their interest in neo-Nazi terminology was uncovered on Facebook in the U.S. last February, following a similar investigation by the Los Angeles Times, and that social network took steps to rectify the situation.