Jeff Bezos may meet his match in Margrethe Vestager

Amazon has faced some raucous critics in recent months—Bernie Sanders and President Donald Trump among them—but somehow their bark always seems worse than their bite. Not so with Margrethe Vestager, the EU’s competition commissioner, who has taken on the likes of Google and Apple with ceaseless intensity, single-minded in her assertion that the reining in of American tech giants is long overdue.

Today Vestager said she has set her sights on Amazon, and Jeff Bezos should probably start worrying now. While the EU has not formerly opened a case against the Seattle e-commerce behemoth, Vestager said at a news conference that her office is in the early stages of gathering information, CNN reported.

EU regulators are concerned that large online retailers may be using data from smaller rivals to give themselves a competitive advantage. “Do you then also use this data to do your own calculations, as to what is the new big thing, what is it that people want, what kind of offers do they like to receive, what makes them buy things?” Vestager said.

Nowhere is that concern more salient than with Amazon, which not only sells its own products but also hosts a thriving ecosystem for third-party sellers—a quarter of which reside outside the United States.

Amazon declined to comment.

EU regulators have been far less kind to American tech giants than those at home. Google was recently hit with a steep fine of $5 billion over accusations that its Android device strategy gave it an unfair advantage.