Vestager hinted on Wednesday that the company could soon be hit with a third hefty fine, Reuters reported.
Google has already been hit with two massive fines by the EU. In June 2017, Google was fined €2.42 billion (US$2.7 billion) for allegedly abusing its search engine dominance to give illegal advantage to its own comparison shopping service. The company has appealed against this fine.
And then in July, the EU imposed a fine of €4.34 billion (US$5.05 billion, A$6.82 billion) on Google for allegedly breaching anti-trust rules over its Android mobile operating system.
Vestager made her comments on Wednesday at the Web Summit in Lisbon when asked for the latest on the probe.
Companies that breach EU rules can be fined up to 10% of their global turnover by Vestager.
The EU has also proposed that big technology companies be taxed on their revenue, and not profit, but that proposal has been opposed by some countries.
In the meantime, Australia's Treasury has made a similar proposal, which is yet to be considered by the Federal Government.