Google faces new federal antitrust probe.

U.S. regulators are in the early stages of an antitrust probe into whether Google Inc, the top player in Web display advertising, breaks antitrust law in how it handles some advertising sales, a source told. The source said that it was unlikely that the Federal Trade Commission had sent out civil investigative demands in relation to the probe, which would be the sign of a formal and more serious investigation.

The new line of inquiry focuses on tools acquired when Google bought display ad company DoubleClick in 2007; other firms which specialize in helping Web publishers sell ads to put on their websites are complaining to the FTC, the source said. The firms have accused Google of leveraging some of its most popular DoubleClick products, such as the ad managing system which has an estimated 80 percent of the market, to push websites to use other products, including Ad Exchange where websites swap ads, the source said. According to a second source familiar with the situation, Google has not been notified of any antitrust investigation so far. Google and the Federal Trade Commission declined comment on the matter.