The top European regulator opened an antitrust investigation into Google on Tuesday, following allegations that the Internet giant has abused its dominance in online search.
The move follows complaints by specialized search-related companies about "unfavorable treatment of their services in Google's unpaid and sponsored search results," the European Commission said in a statement.
The commission said that it was also looking into whether Google may have given its own services "preferential placement" in search results.
The investigation goes beyond the scrutiny the U.S. company so far has received in the United States. Authorities there have been examining Google's acquisitions and actions for indications that its market power may be anti-competitive, but have so far not brought any formal proceedings.
Google is already facing separate antitrust inquiries in Italy, Germany and France.
The European Commission said it would "conduct an in-depth investigation of the case as a matter of priority," noting that it did not yet have "proof of infringements."
In a statement, Google said it has strived to "do the right thing by our users and our industry," such as "ensuring that ads are always clearly marked, making it easy for users and advertisers to take their data with them when they switch services, and investing heavily in open source projects.
"But there's always going to be room for improvement, and so we'll be working with the commission to address any concerns," the company said.
The main thrust of the broader European investigation will be on the online marketplaces for advertising that have emerged in recent years. Google has become a powerhouse by helping advertisers and publishers offer advertising space on the Internet.
In its statement, the commission said it would investigate whether Google had unfairly lowered the rankings of competitor search services, such as those that offer price comparisons of consumer goods.
In particular, the commission said it would look into allegations that Google manipulated a so-called Quality Score that helps to determine how much advertisers pay Google.