The U.S. Federal Trade Commission is reportedly expanding its antitrust probe of Google to include scrutiny of its new Google+ social networking service. The competition issues raised by Google+ go to the heart of the FTC's investigation into whether the company is giving preference to its own services in search results and whether that practice violates antitrust laws, Bloomberg reported on Friday, citing two people related with the probe. Reuters also confirmed Bloomberg's report, citing another source.

Google this week introduced changes to its search engine so that results feature photos, news and comments from Google+, naming the new function "Search, Plus Your World." Users who opt for Google+ see personal information about their friends included from the social networking service when they enter a query.

The Electronic Privacy Information Center urged the FTC to investigate Google for the search changes, according to a Jan. 12 letter posted on its site.

Twitter also complained in a public statement on Jan. 10 that changes in Google's search engine could make finding Twitter posts on news events more difficult.

FTC's broad invertigation on Google's practises is related to whether Google unfairly ranks search results to favor its own businesses and increases advertising rates for competitors.

The agency also is examining whether the company is using its control of the Android mobile operating system to discourage smartphone makers from using rivals' applications.