Google has reportedly returned to the display ads hot seat with the Federal Trade Commission, after avoiding disciplinary action following an antitrust probe that concluded in January.

Citing anonymous sources, Bloomberg is reporting that the investigation is "in the preliminary stages and may not expand into a larger probe." At issue is whether Google is using its role in the online display ad industry (which overall sees $17.7 billion in annual revenue in the U.S.) to force companies to adopt other Google services. The practice can violate antitrust laws, Bloomberg's sources said.

Requests for comment from Google and the FTC were not immediately returned.