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The inquiry is reportedly concerned with whether Google prioritized its own apps over those of others, but may not result in a case being brought against the Californian company, according to Bloomberg. The investigation is apparently being spearheaded by the Federal Trade Commission (FTC), which has previously investigated Google over search.
We've reached out to Google and the FTC for comment, and will update this story when they respond.
Google's Android is the dominant operating system in the US (and indeed, across the world). According to data from Kantar Worldpanel, Android devices accounted for 65.6% of all smartphones sold in the country in the three months ending July 2015. The question is whether Google is using this leading position to push its own products on its operating system (e.g. Chrome Browser, Google Maps) at the expense of its competitors (like Firefox, or Bing Maps).
Google is also facing regulatory scrutiny in Europe. It is accused of abusing its dominant position in search and Android to promote its own products, and is the subject of a European Commission antitrust case. The company denies this, calling the claims "wrong as a matter of fact, law and economics."
And in India, the local regulator sent the search giant a report in late August "outlining its concerns about search dominance and anticompetitive behaviour," The New York Times reports.