The Singapore Democratic Party says that Google refused their request to buy ads on the site

KEY POINTS The Google investigation is part of a broader antitrust inquiry of tech giants

Lawmakers have pushed the breakup of the major technology companies

Google ad revenue totaled $134.8 billion in 2019

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The Justice Department reportedly has zeroed in on Google’s online ad tools in its antitrust investigation of the search giant.

The Wall Street Journal reported Wednesday investigators have reached out to advertising technology firms and agencies to determine how Google’s advertising business works with publishers and advertisers.

The Google investigation is part of a more far-reaching inquiry that includes Amazon, Apple and Facebook. Lawmakers, including Democratic presidential candidate Sen. Elizabeth Warren of Massachusetts and Republican Sens. Ted Cruz of Texas and Josh Hawley of Missouri, have called for the big tech firms to be broken up.

The Journal said nearly all major news publications use Google’s advertising exchange and DoubleClick for Publishers, which was rebranded in 2018 as Google Ad Manager.

Digital advertising is just one aspect of Google’s business that is under Justice scrutiny. Antitrust investigators also are studying its search engine dominance and its effect on other search and mobile businesses like Yelp, Duck Duck Go and Oracle, the Journal said, adding its publisher, News Corp., was among the companies contacted in relation to the advertising probe.

The Journal said of particular interest is Google’s integration of its ad server with its ad exchange and the requirement that advertisers to Google’s tools to place ads on such sites as YouTube. The software is used to buy and sell ads all over the internet, giving Google the ability to monetize digital content. Publishers and rivals in advertising argue it gives Google an anticompetitive advantage, especially on its owned sites.

Google maintains its ad tools give consumers a better experience.

“They are zooming in on the right topics, and that’s a good thing,” Michael Nevins, chief marketing officer of Smart AdServer, which has a rival ad technology, told the Journal.

Google ad revenue totaled $134.8 billion in 2019.

The Associated Press reported Tuesday Assistant Attorney General Makan Delrahim, who was leading the Google investigation, recused himself because he lobbied on Google’s behalf when it faced investigation over its DoubleClick acquisition. The Google investigation now is being led by Associate Deputy Attorney General Ryan Shores.

Fifty state attorneys general also are involved in the investigation. The company, owned by Alphabet (GOOG), was fined $2.72 billion in 2017 by European regulators for abusing its domination of the online search market ant $5 billion in 2018 for antitrust violations involving its Android mobile operating system.