WASHINGTON – The Justice Department has hastened an investigation into Google’s digital advertising practices and could file an antitrust lawsuit against the internet giant before the end of the year, two people with knowledge of the government’s mindset said Wednesday.

The investigation focuses on Google’s power in the digital ad market and examines how the company is using its dominance in auctions and ad technology to assert its power, said those who were not allowed to speak publicly. In recent weeks, the Ministry of Justice has called in other third parties as witnesses and asked for documents and interviews, a sign that it has accelerated the investigation, it said from the population.

The department declined to comment. Google said on Wednesday that there is “tremendous competition in advertising tools that has made online ads more relevant, lowered fees and expanded options for publishers and advertisers”.

Bloomberg had previously reported on the possible lawsuit.

If the Justice Department follows up on the lawsuit, it will be the federal government’s second against Google. In October, the ministry filed an antitrust lawsuit in federal court alleging that Google had abused its monopoly on Internet searches to harm competitors and consumers.

A second lawsuit would also be a show of force by the Biden government to curb the power of big tech companies. President Biden has appointed critics from Amazon, Apple, Facebook and Google to the highest antitrust authorities in the government. In July, he appointed Jonathan Kanter, who represented Google rivals Yelp and Microsoft, to head the Justice Department’s antitrust division. The nomination of Mr. Kanter requires confirmation from the Senate.

Mr. Biden’s antitrust officers have taken up the decisions of the Trump administration to initiate landmark antitrust lawsuits against technology giants. Aside from the search lawsuit against Google, the Federal Trade Commission sued Facebook last year, accusing it of abusing its power over social networks. After a judge dismissed the case, the FTC resubmitted it.

At Google, the Ministry of Justice initially focused on the search, but also investigated whether the company had abused its dominance in digital advertising. Dozens of media companies, advertisers, and ad technology companies have alleged that Google’s advertising practices are anti-competitive. Google operates various parts of digital advertising auctions, including buying ads for marketers and selling ad space by publishers.

The agency is investigating allegations that Google and Facebook entered into an illegal agreement to manipulate the online auctions, the people with knowledge of the situation said.

Texas has cited a lawsuit filed by several attorneys general accusing Google of abusing competition in advertising technology. It was unclear whether the Justice Department would join the state’s lawsuit.