In a statement on Thursday, the EU said “the European Commission services sent to X a formal request for information under the Digital Services Act (DSA)”.
“This request follows indications received by the Commission services of the alleged spreading of illegal content and disinformation, in particular the spreading of terrorist and violent content and hate speech. The request addresses compliance with other provisions of the DSA as well.”
In his letter to Musk, Breton said "violent and terrorist content" had not been taken down from X, despite warnings.
Breton did not give details on the disinformation he was referring to in the letter, but said instances of "fake and manipulated images and facts" were widely reported on the social media platform.
Responding on X, Musk said: "Our policy is that everything is open and transparent, an approach that I know the EU supports.
"Please list the violations you allude to on X, so that the public can see them."
X chief executive Linda Yaccarino also said earlier on Thursday the platform had removed hundreds of Hamas-affiliated accounts and taken action to remove or label tens of thousands of pieces of content since Saturday's attack.