Shares of Google Inc fell nearly 3 percent on Tuesday, following a Bloomberg report that the U.S. Federal Trade Commission is considering an antitrust investigation of the company's dominance of the Web search industry.

Before deciding whether to launch such an investigation, the FTC is waiting for the Justice Department to decide whether it will challenge Google's planned $700 million purchase of airline ticketing software company, ITA Software Inc, Bloomberg reported on Monday, citing people familiar with the matter.

Google's stock was down $16.07 or 2.7 percent at $571.61 on Tuesday afternoon on the Nasdaq.

A potential U.S. probe, which would come on top of an ongoing European antitrust investigation, underscores the increasing non-operational risks that Google is facing, said BGC Partners analyst Colin Gillis.

Google is definitely in the regulatory crosshairs, he said.

News of the possible probe comes a day after Google co-founder Larry Page officially took the reins as CEO after a decade under Eric Schmidt. Schmidt is now executive chairman and will focus on government relations, among other duties.

Google's dominance in search is inviting heightened regulatory scrutiny around the world.

The Internet giant, which runs the world's most popular search engine, has been under investigation by the European Commission since last November.

Last week rival Microsoft Corp filed a formal complaint with European antitrust regulators, claiming that Google systematically thwarts Internet search competition.

Google said in an emailed statement that competition is one click away on the Internet, and that the company works hard to put its users' interest first and to give them the best search results.

A representative for the FTC said the commission had no comment.

The FTC and the Justice Department share responsibility for investigating antitrust claims and could negotiate which agency would lead a major investigation into Google, Bloomberg said.

The Justice Department could soon announce its decision on Google's purchase of ITA, the people told the news agency.

(Reporting by Maria Aspan; Editing by Matt Driskill and Matthew Lewis)