European Union regulators hit Google with a $1.69 billion fine on Wednesday for blocking rival online search advertisers, marking the company's third penalty in two years.

Margrethe Vestager, the E.U.'s competition commissioner, announced the results of the long-running probe of Google's AdSense advertising business case at a news conference in Brussels on Wednesday.

"Google has cemented its dominance in online search adverts and shielded itself from competitive pressure by imposing anti-competitive contractual restrictions on third-party websites," Vestager said.

It's the third time the commission has slapped Google with an antitrust penalty, following multibillion-dollar fines resulting from separate probes into two other parts of the Silicon Valley giant's business.

The third @Google case: @Google is fined €1,49bn for illegal practices in search advertising brokering to cement its dominant market position. They shouldn’t do that - it denied consumers choice, innovative products and fair prices. — Margrethe Vestager (@vestager) March 20, 2019

Last year, the E.U. imposed a record $5 billion fine on Google for using its popular Android mobile operating system to block rivals. This followed a $2.7 billion fine in 2017 for hindering rivals of shopping comparison websites.

While the fines are sizable compared to previous penalties against other companies, they are dwarfed by Google's revenues, which stood at $136.8 billion in 2018.

Vestager gave a cautious welcome to Google's attempts to boost rivals and offer Android users a choice of browser and search apps in order to comply with her orders in those separate cases.

"We see positive developments both in the shopping and Android case," Vestager told the news conference.

In a sign that the tech giant's regulatory troubles may not be over, however, Vestager said she was still looking into its actions in the search market for jobs and local search following complaints.

The most recent fine comes as large U.S. tech companies are facing growing scrutiny in the U.S. Earlier in March, Sen. Elizabeth Warren, D-Mass., put forward a plan to break up Facebook, Google, Amazon and other big tech companies in an effort to increase competition in the tech industry.

The Federal Trade Commission, the government regulator tasked with overseeing competition between tech companies, started a task force in February to increase oversight of the industry.

The FTC, however, has rarely fined tech companies for anticompetitive practices. In 2012, the E.U. fined Google $2.7 billion for favoring its own services — a move that was not matched by the FTC, despite the regulator's staff saying they found "real harm to consumers and to innovation" in Google's business practices.