More than half of America's state attorneys general are set to announce a new probe into Google over possible antitrust violations in a huge escalation against Big Tech.

According to The Washington Post, the investigation is expected to be announced Sept. 9 at a press conference in Washington, but it's not clear whether some of the officials will also open or announce plans for probes into other tech companies, like Amazon and Facebook.

It's been a difficult year for the Silicon Valley mainstays, which have come under increasing scrutiny for their practices around data collection, content policing and their amassing of political and economic power.

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The Department of Justice and the Federal Trade Commission are broadly investigating antitrust concerns posed by Silicon Valley. Facebook disclosed in July that the Federal Trade Commission (FTC) had opened an antitrust probe against it earlier this year.

Several 2020 presidential candidates, most prominently Sen. Elizabeth Warren, D-Mass., have called for Big Tech giants to be broken up for alleged anticompetitive behavior.

In addition, a new bill in the Senate called the "Monopolization Deterrence Act" would impose crippling fines on tech giants -- ranging as high as 15 percent of the firm's total U.S. revenues -- if they were found to be in violation of antitrust law.

Silicon Valley is facing regulatory pressure from a range of different agencies and lawmakers on both sides of the Atlantic Ocean. (Fox News)

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"Google's services help people every day, create more choice for consumers, and support thousands of jobs and small businesses across the country," a Google spokesperson told Fox News in an emailed statement. "We continue to work constructively with regulators, including attorneys general, in answering questions about our business and the dynamic technology sector."