European Union antitrust regulators may order Alphabet’s Google to sell a part of its advertising-technology business, a source with direct knowledge of the matter told Reuters on Monday.

Google’s dominance in online advertising has been increasingly questioned over the past few years. Complaints from rivals about its allegedly anti-competitive practices have led to antitrust investigations in multiple continents concerning its practices.

The European Commission, which launched an investigation into Google’s ad-tech business in 2022, said at that time that it was concerned about Google’s presence at almost all levels of the supply chain for online display advertising.

Break-up orders from the EU competition enforcer are rare. However, frustration has been mounting after Google failed to address competition concerns, the source said.

The Commission and Google did not immediately respond to Reuters’ requests for comment.

The move was first reported by the Wall Street Journal on Monday.