Sources said that the five-member commission is preparing to send Google the formal demands for information within days. Other companies are also likely receive official requests for information about their dealings with Google at a later stage, they said.
Representatives for Google and the FTC declined to comment.
From Google's perspective, the FTC's embryonic antitrust probe is the most serious to date in the U.S. Although Google has faced numerous antitrust investigations in recent years, at least in the U.S., federal inquiries have so far largely been limited to reviews of its mergers and acquisitions.
The new FTC investigation, by contrast, will examine fundamental issues relating to Google's core search advertising business, which still accounts for the overwhelming majority of its revenues. Those will include whether Google—which accounts for around two-thirds of internet searches in the U.S. and more abroad—unfairly channels users to its own growing network of services at the expense of rivals'.
In November, the European Commission opened its own formal investigation into allegations by several companies that it had violated European competition laws.