The Federal Trade Commission has reportedly focused its antitrust investigation on Google's Android operating system and its online search methods.

In June, Google confirmed that U.S. antitrust regulators were launching a probe, but said it was unclear about the FTC's specific concerns.

It looks as though a large part of the investigation will be to determine if Google prevents smartphone manufacturers that use its Android OS from using competitors' services, reports the The Wall Street Journal.

The FTC's investigation into Android addresses concerns that Google uses its market power to force smartphone makers to use its services over those of competitors. One example is Skyhook Wireless, who recently filed suit against Google saying it pressured device makers into using Google's location-based technology instead of Skyhook's.

Other concerns center around Google being the default search engine for many smartphones that use the Android OS. Canalys, a research company, said Android was the default search engine for almost half of the smartphones shipped last quarter, and the FTC is questioning whether that helps Google maintain its healthy lead in Web search.

As we reported yesterday, Google’s search engine had 65 percent of the U.S. searches in July, while Microsoft’s Bing had a 14.4 percent market share, according to a new report from comScore.

Of course, users aren't forced to use any Google product and can readily choose the Bing search engine over Google's on an Android-based smartphone. This is one of the reasons why ZDNet's Larry Dignan believes the investigation into Android is likely to hit a dead end.

As we noted in June, the FTC also is investigating accusations that Google engages in anti-competitive behavior that promotes its own products and services over that of competitors, as well as scraping and using other companies' content. The WSJ reports that Google has already made some changes to its search results to assuage competitors' concerns.

The investigation will likely take at least a year to complete.

It's interesting to note that the Justice Department also recently launched an antitrust investigation in which Google is also involved. However this probe is to determine if Google itself is an antitrust victim and if the recent $4.5 billion Nortel patent sale to Microsoft and others would unfairly hurt smartphone makers that use Google's Android operating system.