WASHINGTON — Lawmakers investigating the market dominance of Big Tech on Friday asked Google, Facebook, Amazon and Apple for a broad range of documents, marking a step forward in Congress’ bipartisan probe of the companies.

Letters went out to the four companies from the leaders of the House Judiciary Committee and its subcommittee on antitrust, which has been conducting a sweeping antitrust investigation of the companies and their impact on competition and consumers. The lawmakers are seeking a detailed and broad range of documents related to the companies’ sprawling operations, including top executives’ internal communications.

The move comes as scrutiny of the big tech companies deepens and widens across the federal government and U.S. states and abroad. The Justice Department and the Federal Trade Commission are conducting competition investigations of the companies, and state attorneys general from both major political parties have opened antitrust investigations of Google and Facebook. The probe of Google has drawn participation by 50 states and territories.

“We have to act if we see that they’re breaking the law,” Rohit Chopra, one of the FTC commissioners, said Friday in an interview on CNBC. Chopra, a Democrat, wouldn’t confirm specifically names of companies that could be under investigation, but he said the agency is consulting closely with the Justice Department and the state attorneys general as their work proceeds.

Also Friday, the European Union’s powerful competition chief indicated that she’s looking at expanding regulations on personal data, dropping an initial hint about how she plans to use new powers against tech companies. Margrethe Vestager said that while Europeans have control over their own data through the EU’s world-leading data privacy rules, they don’t address problems stemming from the way companies use other people’s data “to draw conclusions about me or to undermine democracy.”

The House lawmakers set an Oct. 14 deadline for the companies to provide the documents.

Spokesmen for Facebook, Apple and Amazon didn’t immediately respond to requests for comment Friday. Google referred to a recent blog post by its senior vice president for global affairs, Kent Walker, saying the company is anticipating additional questions from investigations and that “We have always worked constructively with regulators and we will continue to do so.”

The companies have said they’ll cooperate fully with the congressional investigation.

Judiciary Committee Chairman Rep. Jerrold Nadler, D-N.Y., said the documents will help the committee understand “whether they are using their market power in ways that have harmed consumers and competition and how Congress should respond.”

The letters went to the four companies’ CEOs: Larry Page of Google’s parent company Alphabet Inc.; Mark Zuckerberg of Facebook; Jeff Bezos of Amazon; and Tim Cook of Apple. They were signed by Nadler; Rep. Doug Collins of Georgia, the Judiciary Committee’s senior Republican; Rep. David Cicilline, D-R.I., who heads the antitrust subcommittee leading the investigation; and Rep. James Sensenbrenner of Wisconsin, the subcommittee’s senior Republican.

Cicilline has said Congress and antitrust regulators wrongly allowed the big tech companies to regulate themselves, enabling them to operate out of control, dominating the internet and choking off online innovation and entrepreneurship. He has suggested legislative changes may be needed, though he has called breaking up the companies a last resort.

At a hearing of the antitrust panel in July, executives of the four companies pushed back against lawmakers’ accusations that they operate as monopolies, laying out ways in which they say they compete fairly yet vigorously against rivals in the marketplace.

Cicilline said he was dissatisfied with the answers the executives gave to lawmakers’ questions, calling their testimony “evasive.”

The letter to Facebook requests a breakdown of company profits since 2016 on its top products — including Facebook Ads, Instagram and WhatsApp. It also seeks communications from Zuckerberg and other top executives related to a California court case in which plaintiffs accuse the company of deceptively crushing thousands of apps in 2015 whose businesses had relied on their platform. Among other internal communications the letter seeks are those related to six messaging, video- and photo-sharing apps in particular that Facebook cut off.

The lawmakers are seeking Facebook executives’ emails on the decision to deny any specific apps or categories of apps access to Facebook data about or shared by users. This is a concern because critics say the company intentionally walled itself off from other online apps, enabling it to amass nearly 2.5 billion users with no clear competitor.

The letter to Alphabet seeks detailed financial information and names of leading competitors for Google’s vast operations, including search, video service YouTube, the Android cellphone operating system and Gmail. Internal communications the lawmakers are seeking include those related to Google’s 2007 acquisition of online advertising company DoubleClick — which critics often point to as pivotal to Google’s advertising dominance.

For Amazon, the lawmakers seek financial data and competitor names for Amazon Web Services, smart speakers Alexa and Echo, Amazon Prime, Whole Foods and other properties, as well as on its online retail, on-demand movie and music streaming, digital advertising and cloud computing operations. A 2018 agreement with Apple to sell Apple products on Amazon and to limit the resellers that can sell Apple products on Amazon is among the decisions being examined.

Financial information and competitors are sought for Apple’s App Store, iPhone, iPad, Mac, Siri, Apple Pay, Apple TV and Apple Watch. The lawmakers are interested in Apple’s decision to remove from the App Store or to impose restrictions on some screen-time and parental-control apps, and on the App Store algorithm that determines the ranked order of search apps on the site, among other areas.

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