The relationship between Elon Musk and the European Union deteriorated further on Monday, with the bloc launching a formal investigation into the way X has been run since the billionaire took over last year.

Senior officials from the European Commission said they were concerned about a range of new features that have been added to X under Musk, as well as the way violent content related to the Hamas attack on Israel was allowed to spread without consistently being labeled with a graphic content warning.

EU officials also said they would be investigating whether users on the platform are being misled about the trustworthiness of people who pay for blue checkmarks—a feature that was previously reserved for verified users such as celebrities, public figures, or journalists. Since Musk’s takeover, the platform has allocated blue checks to paying subscribers, a feature that researchers say has been leveraged to spread scams and disinformation.

Another focus for the investigation is whether Community Notes—X’s crowdsourced fact-check program—can work in languages other than English or intervene fast enough during elections.

Other concerns raised by the EU include the way users can notify X when they have seen illegal content and whether the platform is too focused on the English language in its content moderation operations. X has more than 2,000 English-speaking moderators, but only one Dutch-speaking moderator and one Polish moderator, according to a tally the company released last month.

With the investigation, X becomes the first major platform to face a formal probe for violating rules included in the European Union’s new Digital Services Act, which has the power to tell tech companies to change the way they operate or fine them up to 6 percent of their global revenue. “Today’s opening of formal proceedings against X makes it clear that, with the DSA, the time of big online platforms behaving like they are ‘too big to care’ has come to an end,” said Thierry Breton, the EU’s internal markets commissioner. An in-depth investigation will now take place.

“X remains committed to complying with the Digital Services Act,” company spokesperson Joe Benarroch told WIRED, adding that the platform is cooperating with regulators. “It is important that this process remains free of political influence and follows the law.”