The U.S. Federal Trade Commission has opened an in-depth antitrust probe of Meta’s plan to buy the popular VR fitness app Supernatural, according to a new report by The Information.

The probe means that antitrust regulators are starting to scrutinize the-company-formally-known-as-Facebook’s interest in scooping up VR startups, not just its traditional social media acquisitions. According to The Information’s Josh Sisco, Meta’s previous five virtual reality acquisitions, including its deal for the studio behind hit game Beat Saber, weren’t probed by the government because the purchase prices were too small. “But those regulators are slowing down the $400 million-plus Supernatural deal, according to two people with knowledge of the situation,” the report notes.

It’s unclear what criteria the FTC, which is simultaneously suing Meta in a bid to unwind the acquisitions of Instagram and WhatsApp, is using to evaluate the VR deal. VR is a nascent but fast-growing industry that third-party estimates say Meta has a majority market share of, thanks mostly to the early success of its Quest 2 headset. While the FTC might eventually approve the Supernatural deal, its decision to investigate signals that Meta’s playbook of quickly buying the hottest VR startups on its platform may already be coming to an end.