European regulators announced Tuesday that they had launched a formal antitrust investigation of Google Inc. to determine whether it has abused its search-engine dominance to squelch online rivals.
The inquiry was triggered by complaints from some websites that Google treated their results differently from its own in displaying unpaid and sponsored search results, the European Commission said.
"This initiation of proceedings does not imply that the commission has proof of any infringements. It only signifies that the commission will conduct an in-depth investigation of the case as a matter of priority," the commission said.
Google said in a statement Tuesday that it would cooperate with the commission's investigation.
"Since we started Google we have worked hard to do the right thing by our users and our industry -- ensuring that ads are always clearly marked, making it easy for users 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.
Google acknowledged previously that European competition regulators had contacted it about complaints received from three websites -- Britain's Foundem, a price comparison site; France's ejustice, a legal search engine; and Ciao! from Bing, a product rating site run by Microsoft Corp. in several European countries.
"While we will be providing feedback and additional information on these complaints, we are confident that our business operates in the interests of users and partners, as well as in line with European competition law," Google's senior competition counsel, Julia Holtz, wrote on the company's European Public Policy blog in February.
"Though each case raises slightly different issues, the question they ultimately pose is whether Google is doing anything to choke off competition or hurt our users and partners. This is not the case."
European regulators said they will investigate whether Google lowered the ranking of unpaid search results of competing services, such as price comparison, and gave its own services "preferential treatment ... in order to shut out competing services."
The inquiry also will look into complaints that Google lowered the so-called "Quality Score" for sponsored links of competing services, which would affect the price paid by advertisers.
And the European Commission said it will probe allegations "that Google imposes exclusivity obligations on advertising partners, preventing them from placing certain types of competing ads on their websites, as well as on computer and software vendors, with the aim of shutting out competing search tools."