The U.S. Federal Trade Commission is considering opening up a new antitrust probe into Google’s businesses practices once again, according to reports. This one would not be into Google’s search business, but its display advertising business.

Bloomberg cites sources who wished not to be named, as saying the FTC is in the “preliminary stages” of a probe into whether the company “is using its leadership in the online display-advertising market to illegally curb competition,” but that it “may not expand into a larger probe.” Bloomberg’s Brian Womack and Sara Forden report:

FTC investigators are examining whether Google is using its position in U.S. display ads — a $17.7 billion industry that includes the sale of banner ads on websites — to push companies to use more of its other services, a practice that can be illegal under antitrust laws, the people said.

A similar report has come out from Reuters, who says its source said, “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.” Reuters reports:

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.

Google, which is not commenting on the prospect of a new investigation has apparently not been contacted about one.

Google continues to face various antitrust probes around the world, including in Europe, Canada, Argentina and South Korea.