WASHINGTON — A congressional antitrust investigation into Apple, Amazon, Facebook and Google entered a new phase Friday, Sept. 13, after lawmakers called on each of the tech giants to turn over a trove of sensitive documents, including top executives' private communications.

The requests sent by Democrats and Republicans on the House Judiciary Committee ask the companies to share detailed information about their internal operations, including copies of key communications between top-level executives about potential merger targets and records related to "any prior investigation" they have faced on competition grounds.

With Google, for example, Democratic and Republican lawmakers are seeking a fuller understanding of the company's decades-long efforts to build an dominant footprint in search and advertising.

They've asked Google's parent company, Alphabet, to turn over internal emails and other records related to its prior mergers, such as its purchase of YouTube, along with documents they've turned over to other governments in connection with previous antitrust investigations of the tech giant. Google has faced multiple such investigations in recent years, especially in the European Union, which has fined the company more than $9 billion for violating competition laws.

With Facebook, meanwhile, lawmakers asked the social-networking giant to turn over records in which Mark Zuckerberg, the company's chief executive, might have talked about corporate rivals, including the since-shuttered app Vine and two services Facebook later acquired, Instagram and WhatsApp. Investigators also are seeking additional documents related to Facebook's relationships with third-party app developers.

The bipartisan requests arrive from the House Judiciary Committee's top antitrust panel, led by Chairman David Cicilline, D-R.I., and James Sensenbrenner, R-Wis. They are not official legal demands, though the panel does have key powers to compel Apple, Amazon, Facebook and Google to turn over records or appear at hearings if necessary. (Amazon founder Jeff Bezos owns The Washington Post.)

The companies did not immediately respond to requests for comment.

"The open Internet has delivered enormous benefits to Americans, including a surge of economic opportunity, massive investment, and new pathways for education online," Rep. Jerry Nadler, D-N.Y., the chairman of the full Judiciary Committee, said in a statement. "But there is growing evidence that a handful of corporations have come to capture an outsized share of online commerce and communications."

His Republican counterpart, Rep. Doug Collins, added: "This information is key in helping determine whether anticompetitive behavior is occurring, whether our antitrust enforcement agencies should investigate specific issues and whether or not our antitrust laws need improvement to better promote competition in the digital markets."

The demands from House Democrats and Republicans add to the antitrust pressure on Silicon Valley, as regulators around the country begin to question whether tech giants threaten innovation, smother new start-ups and result in higher prices or worse online services for consumers.

On Monday, attorneys general from nearly every U.S. state and territory announced an investigation into Google, focusing initially on the online-advertising machine that powers its search engine and bottom line. The company is also facing a probe by the Department of Justice, part of a broad look at the competition issues posed by the tech industry. State and federal authorities each have issued Google formal legal demands for records related to their investigations.

A week earlier, 11 state attorneys general said they'd open a competition-minded probe of Facebook, including the way it taps billions of users' personal data. In Washington, the Federal Trade Commission is also exploring the company, focused on its prior acquisitions, an outgrowth of the FTC's wide-ranging review of the industry.

House lawmakers launched their investigation in June: Cicilline at the time described the internet as "broken," before highlighting the "reluctance in the early days of the Internet to interfere" among government. A month later, the Judiciary Committee grilled officials from Apple, Amazon, Facebook and Google at a hearing, where Cicilline pointed to a web that had become "increasingly concentrated, less open, and growingly hostile to innovation and entrepreneurship."

On Friday, Cicilline said the committee's requests for information marked an "important milestone in this investigation."

"We expect stakeholders to use this opportunity to provide information to the Committee to ensure that the Internet is an engine for opportunity for everyone, not just a select few gatekeepers," he said.

This article was written by Tony Romm, a reporter for The Washington Post.

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