Google on Friday confirmed that the US Federal Trade Commission (FTC) is investigating the online giant for antitrust violations related to its search and advertising business practices. The company pledged to cooperate with the investigation.

"It's still unclear exactly what the FTC's concerns are, but we're clear about where we stand," Google Fellow Amit Singhal wrote in a blog post acknowledging the investigation. "Since the beginning, we have been guided by the idea that, if we focus on the user, all else will follow. No matter what you're looking for [online], we want to get you the information you want as quickly as possible."

According to a terse regulatory filing, Google received a subpoena and a notice of civil investigative demand from the FTC on Thursday, June 23, a day before the company admitted to the federal action against it. The FTC says it will "review Google's business practices, including search and advertising."

The investigation has been a long-running non-secret. According to multiple sources, the FTC has received enough complaints about the online giant's business practices to start a formal investigation. And if this investigation leads to antitrust charges, the result could be an epic federal trial reminiscent of Microsoft's first antitrust trial from over a decade ago.

Its dominance over online search and thus online advertising gives Google power over the competition that is similar to what Microsoft wielded a decade prior. It controls about 66 percent of the online search market in the United States; it's a business that is worth almost $30 billion a year overall. Google's search-based advertising represents virtually all of the company's revenues despite numerous other technology initiatives.

At least one competitor has already saluted the FTC action. FairSearch.org—which represents Google competitors such as Expedia, Kayak, Microsoft, and Travelocity—voiced its support. "Google engages in anticompetitive behavior across many vertical categories of search that harms consumers," a FairSearch.org statement reads. "The result of Google's anticompetitive practices is to curb innovation and investment in new technologies by other companies."

Google says that the principles by which it evolves its search engine will "stand up to scrutiny." And the company has create a new website, Facts about Google and Competition, to help tell its story.