Fresh on the heels of a French investigation into Google’s advertising business, the company may be facing an even bigger threat in the form of an EU investigation.

According to Reuters Google could be about to face its biggest regulatory challenge yet, as the EU is reportedly preparing to investigate the company’s adtech business. The company recently settled with the French Competition Authority, to the tune of $267 million, and vowed to make changes.

It appears EU antitrust regulators may be looking to go further, however, and scrutinize the company’s business far more than the French regulators did, according to Reuters’ sources. The investigation will reportedly begin before the end of the year.

The rumors are especially bad news for Google, as advertising is the bread-and-butter of the company’s revenue, far exceeding any other business division.