The search giant was fined a record $2.72 billion by European regulators in 2017 for abusing its dominance of the online search market. In the U.S., the Federal Trade Commission made an antitrust investigation of Google but closed it in 2013 without taking action.

Now the Justice Department has undertaken an antitrust probe of the company's search and other businesses, according to reports by The Wall Street Journal, The New York Times and Bloomberg News. They cited unnamed people familiar with the matter.

Justice Department spokesman Jeremy Edwards declined to comment Saturday. Google declined any comment.

Google, owned by Alphabet Inc., has faced mounting scrutiny as regulators around the world have focused on tech companies' business practices over the past year. In addition to the 2017 record fine, European regulators also slapped a $1.7 billion penalty on the company in March for barring websites from selling ads from rivals alongside some Google-served ads near search results.

Google says it has now ended that practice.

The company made changes voluntarily when the FTC shut down its investigation, including letting advertisers use information from their Google ad campaigns to create campaigns with rivals.

But an FTC staff report that was released years later showed that the agency staff had urged the presidentially-appointed commissioners to bring a lawsuit against Google. That never happened.

Google commands the lead in digital ad revenue by a wide margin, controlling 31.1% of global digital ad dollars, according to eMarketer's 2019 estimates. Facebook is a distant second with 20.2%.

Politicians and outside antitrust analysts have expressed concern in recent years that Google controls too much of the digital ad process. It makes the technology, hosts the largest search site where ads appear and collects data from all ad campaigns that it runs.