Staffers from the antitrust office have interviewed multiple Google competitors about its practices in the advertising technology market, putting a target on the company’s second-most important business, according to people familiar with the action, who asked not to be identified discussing the early stage probe.

The Justice Department already sued Google last year, saying the Alphabet Inc.-owned company was abusing its dominance in internet search, its biggest business. Any additional legal action, including whether to bring a second suit, will likely depend on whoever is chosen as the assistant attorney general of the antitrust division by U.S. President Joe Biden. It will be up to that person to decide whether to proceed, and it’s possible the government will bring no action against the company.

The government is also gathering evidence from existing lawsuits and probes in other jurisdictions, focusing on Google’s business that places ads on others’ websites, one of the people said. The Justice Department declined to comment.

“Our advertising technologies help websites and apps fund their content and enable small businesses to reach customers around the world,” Julie Tarallo McAlister, a Google spokeswoman, said in a statement. “The enormous competition in online advertising has made online ads more relevant,reduced ad-tech fees, and expanded options for publishers and advertisers.”

Google, which for many serves as the home page of the internet, has been under intense antitrust scrutiny from regulators around the world, who have opened a flurry of investigations into the company’s business practices. The antitrust division’s continued information-gathering on Google’s display business raises the specter of additional regulatory enforcement against the internet giant in the U.S., its largest market and home turf.

The news comes soon after the confirmation of tech critic Lina Khan as the new chair of the U.S. Federal Trade Commission, as well as the European Union’s announcement of a formal investigation into whether Google has abused its leading position in the ad tech market. The company this month made concessions to the French government to make its digital auctions fairer.

Google already faces three antitrust lawsuits at home, one led by the Justice Department and two brought by coalitions of U.S. state attorneys general.

The Mountain View, California-based company owns major pieces of the online ad market. It runs an ad-buying service for marketers and an ad-selling one for publishers, as well as a trading exchange where both sides complete transactions in lightning-fast auctions.

These exchanges operate like online stock-trading platforms with an automated bidding process. Competitors and publishers have complained that Google leverages parts of this vast network, like its ad exchange, to benefit other areas and kneecap rivals. Overall, these ad tech products generated $23 billion in gross revenue for the internet giant last year. Google has argued that it pays out much of these ad-tech sales to web publishers.

The Justice Department cast a wide net when it began investigating Google under Attorney General William Barr, speaking with longtime foes of the tech giant including News Corp., Oracle Corp., and Yelp Inc. on their varied concerns about Google, including claims related to ad tech. In October, the department sued Google on other grounds, alleging the company had taken anti-competitive steps to extend its search engine monopoly. Two months later, a group of U.S. states led by Texas sued Google, claiming it had rigged the digital ads market, at which point it was unclear if the Justice Department maintained an interest in investigating Google’s ad tech business.

Texas Attorney General Ken Paxton has taken the lead on targeting Google’s display ads business, joined by 14 other states and territories, but has also had to contend with a staff revolt and allegations of corruption. The existing lawsuit claimed that Google had an illegal deal to manipulate digital ad auctions by giving Facebook Inc. access to “information, speed and other advantages” that other market participants didn’t have. Google has denied all wrongdoing.