(Alastair Pike/AFP/Getty Images)

More than half of the nation’s state attorneys general are readying an investigation into Google for potential antitrust violations, scheduled to be announced next week, marking a major escalation in U.S. regulators’ efforts to probe Silicon Valley’s largest companies.

A smaller group of these state officials, representing the broader coalition, is expected to unveil the investigation at a Monday news conference in Washington, according to three people familiar with the matter who spoke on the condition of anonymity because they were not authorized to discuss a law enforcement proceeding on the record, cautioning the plans could change.

It is unclear whether some or all of the attorneys general also plan to open or announce additional probes into other tech giants, including Amazon and Facebook, which have faced similar U.S. antitrust scrutiny. The states’ effort is expected to be bipartisan and could include more than 30 attorneys general, one of the people said.

Over the past year, regulators around the country have grown increasingly wary of the power wielded by Silicon Valley, questioning whether the industry’s access to vast amounts of proprietary data — and deep pockets — allow companies to gobble up rivals and maintain their dominance to the detriment of consumers. Two federal antitrust agencies have opened probes targeting the industry broadly, while lawmakers in Congress have grilled executives from Amazon, Apple, Facebook and Google about the business practices. (Amazon founder Jeff Bezos owns The Washington Post.)

Outside of the nation’s capital, however, state officials also have started questioning the growing influence of big tech. Attorneys general in multiple states have threatened that competition probes could be on the horizon, The Post first reported in March, and states such as Louisiana and Mississippi have sharply criticized Google for its handling of users’ personal information and its algorithms for surfacing search results. Those states did not respond to requests for comment.

Texas officials have raised similar concerns. They have also said that Google may be violating state consumer-protection laws if political bias at Google resulted in the censorship of conservative viewpoints. A spokesman for the attorney general there also did not respond to a request for comment.

Over the summer, some attorneys general met privately with officials from the Justice Department, which announced its own broad review into big tech, to discuss their antitrust concerns. The agency’s antitrust leader, Makan Delrahim, later said at a conference in August that the federal government is coordinating with state leaders, which he numbered at more than a dozen, but declined to offer further details about the agency’s plans.

It is unclear whether the Justice Department will join the states at the event, and a spokesman did not immediately respond to a request for comment.

“Google’s services help people every day, create more choice for consumers, and support thousands of jobs and small businesses across the country,” spokesman Jose Castaneda said in a statement. “We continue to work constructively with regulators, including attorneys general, in answering questions about our business and the dynamic technology sector.”

The states’ looming antitrust investigation of Google threatens to saddle the company with years of regulatory scrutiny, even though the federal government has the most powerful tools at its disposal — including the ability to try to break up a business for violating competition laws.

But state attorneys general can contribute to federal action. For example, in the 1990s, the states helped build a broader case against Microsoft after rivals complained that it leveraged its Windows monopoly as it entered new markets and used it to erect barriers to competitors.

“If multiple states — and I mean not just Democratic attorneys general but Republican attorneys general as well — are all looking into potential antitrust violations, one of the biggest effects might be to pressure the federal government to do a deeper dive,” said Doug Gansler, the former attorney general of Maryland and a top lawyer at the firm Cadwalader, Wickersham & Taft.

For Google, the states’ heightened interest comes about six years after the U.S. government formally studied the tech giant’s search-and-advertising business but opted against slapping it with significant penalties. The inaction in the United States came to stand in stark contrast with Europe, which later issued a series of stinging, multibillion-dollar fines against the company for the way it displays search results and manages its Android smartphone operating system.

The Justice Department and the Federal Trade Commission’s broad reviews into big tech could evolve into more formal probes of Google and its Silicon Valley peers. Senate lawmakers on Tuesday announced they would hold a hearing focused on tech giants that acquire smaller rivals.