Sources tell Reuters that Google (GOOG) is once again under investigation by U.S. regulators for possible violations of antitrust laws.
The latest probe by the Federal Trade Commission (FTC) centers around the Internet search giant’s advertising sales practices. The FTC was not yet thought to have issued formal requests, signaling that the investigation remains in its formative stage. Google has not yet received any notification from regulators.
Complaints from rival online advertising firms may have sparked the new probe. In 2007, Google acquired digital ad firm Doubleclick, making the company the leader in the $15 billion U.S. digital display ad market last year.
Google accounted for 15.1% of the display ad market in 2012, but is expected to increase that share of 20.7% by next year. Its closest rival, Facebook (FB) held 14.6% of the market last year.
U.S. regulators shut down an antitrust investigation of Google earlier this year, ruling that the company was not violating the law in the way it displays search engine results.
Shares of Google fell more than 1% in Friday morning trading.