Microsoft’s purchase of Activision Blizzard has hit another snag, with the EU opening an “in-depth investigation.”

Microsoft announced at the beginning of the year that it was purchasing Activision Blizzard for $68.7 billion, making it one of the biggest deals in tech history. Almost immediately, regulators on both sides of the Atlantic expressed concern over the potential impact of Microsoft — the maker of the Xbox gaming console — owning the publisher of some of the world’s most popular gaming titles.

Although the EU has already been investigating the deal, The Verge is reporting that it is moving to an “in-depth investigation.” The EU Commission plans to carry out its investigation over a period of 90 work days, meaning the deal could be delayed until March 23.

The Commission said it was “concerned that the proposed acquisition may reduce competition in the markets for the distribution of console” and PC titles. The concerns don’t stop there, however, with the Commission afraid that Microsoft owning Activision could even help it shut out rivals in the broader PC market.

“The Commission is concerned that Microsoft may reduce the ability of rival providers of PC operating systems to compete with Microsoft’s operating system Windows, by combining Activision Blizzard’s games and Microsoft’s distribution of games via cloud game streaming to Windows,” the Commission said in a statement. “This would discourage users to buy non-Windows PCs.”

As recently as September, Microsoft CEO Satya Nadella said he was “very, very confident” the deal would be approved. Only time will tell if that sentiment proves true.