Other investigations into the platform’s chatbot are underway in Australia, France and Germany.
Grok was temporarily banned in Indonesia and Malaysia, although the latter has now lifted the ban.
Henna Virkkunen, Executive Vice-President for Tech Sovereignty, Security and Democracy at the Commission called the sexual deepfakes a “violent, unacceptable form of degradation”.
“With this investigation, we will determine whether X has met its legal obligations under the DSA, or whether it treated rights of European citizens – including those of women and children – as collateral damage of its service,” she said.
In a statement to Reuters, Doherty said there were “serious questions” over if platforms such as X were meeting legal obligations “to assess risks properly and to prevent illegal and harmful content from spreading”.
“The European Union has clear rules to protect people online,” she said.
“Those rules must mean something in practice, especially when powerful technologies are deployed at scale.
“No company operating in the EU is above the law.”
The move comes a month after the EU fined X €120m (£105m) over its blue tick badges, saying they “deceive users” because the firm is not “meaningfully verifying” who is behind the account.
In response, the US Secretary of State Marco Rubio and the Federal Communications Commission (FCC) accused the EU regulator of attacking and censoring US firms.
“The European Commission’s fine isn’t just an attack on X, it’s an attack on all American tech platforms and the American people by foreign governments,” he said.
His remarks were reposted by Musk, who added “absolutely”.