The Justice Department on Friday gave the green light to Google’s $400 million acquisition of AdMeld, a major display advertising company.

The agency said the deal can proceed without any conditions, because a detailed analysis by antitrust lawyers found there are enough competitors that offer services similar to AdMeld, a company that helps online publishers sell their ads.

For the past two years, Google has been steadily acquiring dozens of companies in a wider swath of areas, drawing scrutiny from competitors, regulators and some consumer advocates who worry that the company is leveraging its dominance in online searches to expand into other businesses. The deals have run the gamut, with Google purchasing everything from restaurant review business Zagat to cellphone maker Motorola Mobility.

“Although the Antitrust Division concluded that this particular transaction was unlikely to cause consumer harm, the division will continue to be vigilant in the enforcement of the antitrust laws to protect competition in display and other forms of online advertising,” Justice said in a statement.

“We’re pleased that the U.S. Department of Justice has today cleared this deal,” said Neal Mohan, Google’s vice president of display advertising, in a company blog post.

AdMeld did not immediately respond Friday to a request for comment.

Display ads, which include banners that span across Web pages, are a fast-growing business. Google already dominates the sale of text ads that appear next to searches, and is trying to expand into display ads through acquisitions like AdMeld and DoubleClick, which the company bought in 2008.

Each major acquisition by the search titan is getting a close look by antitrust officials. This year, Justice officials approved a controversial deal with ITA Software, which makes technology that powers online flight searches, but added some restrictions on Google’s behavior.

The Justice Department is still looking closely at the company’s $12.5 billion bid to buy Motorola Mobility.

Meanwhile, the Federal Trade Commission is in the middle of a broader investigation of the company’s behavior and its effects on competition.

Although Google is known for its search engine, the company makes its money selling the ads that run alongside search results. In the third quarter, revenue was up 33 percent compared with last year.