SAN FRANCISCO — House lawmakers have asked more than 80 companies for information about how their businesses may have been harmed by Amazon, Apple, Facebook and Google, according to four people familiar with the requests.
The House Judiciary Committee, which is investigating the influence of the tech giants, sent formal requests for information to the companies on Sept. 13.
They were asked about their own businesses and how the four tech companies may have engaged in anticompetitive behavior, according to the people who have seen the requests and spoke on the condition of anonymity because the lawmakers asked to keep the letters private.
The bipartisan requests from the committee indicated the increasing scope of the congressional investigation into Silicon Valley’s power and offered more insight to the pressure Big Tech faces in the coming months. Similar inquiries are underway at the Justice Department, at the Federal Trade Commission and a bipartisan collection of attorneys general from dozens of states.
Lawmakers sent the requests on the same day they asked for scores of documents and personal emails from top executives at the four tech companies, according to the people. All of the companies have until mid-October to respond.
The additional letters to more than 80 companies show the breadth of the offensive forming against Amazon, Apple, Facebook and Google. The recipients of the requests range from smaller firms in retail and advertising to large corporations in entertainment, software and social media, the people said.
A range of companies, including News Corp., Oracle, Spotify, TripAdvisor and Yelp, have complained about the behavior of the four big tech companies and were likely to have received the requests. It was unclear how the queries to the more than 80 companies are split among the four tech giants.
One person familiar with the requests said lawmakers decided against publicizing the requests to protect the complaining companies from potential retribution from the four tech firms — though those firms have said they do not retaliate against critics.
Companies have protested Silicon Valley’s growing size and influence for years, but regulators and lawmakers in Washington have sharply increased their focus on Amazon, Apple, Facebook and Google in recent months.
The House investigation is largely centered on the market power and alleged anticompetitive practices by the four companies. The committee is examining accusations that the big companies favor their own products over rivals, buy smaller firms to head off competition and leverage their size to further cement their dominance.
Lawmakers are also scrutinizing how the companies avoid taxes, are used to spread disinformation and handle people’s personal information.
Amazon, Apple, Facebook and Google have said in the past that they face ample competition and do not engage in anticompetitive practices. When asked on Friday about the letter sent to the more than 80 companies, none of the companies offered additional comment.
The Wall Street Journal reported earlier that House lawmakers had sent requests to some of the tech companies’ rivals.
The various investigations are just beginning in earnest. How far they will go, what they will uncover and whether any allegations will stand up in court are all uncertain.
It is also not clear how the tech companies will defend themselves. On Thursday, Mark Zuckerberg, Facebook’s chief executive, met with President Trump and held discussions on Capitol Hill about election security, privacy and other issues.
Senator Josh Hawley, Republican of Missouri, said on Thursday that it was time for the companies to be more upfront with the public.
“We’ve had a lot of talk from Facebook, and we have a troubling pattern, when they’re up on the Hill, of them saying things that turn out to be either very misleading or at the end of the day it’s just not true or they just don’t follow through on it,” Mr. Hawley said.
The Department of Justice sent Google a formal request for information this year, and Facebook has acknowledged it is the subject of an antitrust investigation by the Federal Trade Commission. When the agencies divided up responsibility for handling competition questions about Silicon Valley this year, the Justice Department also took Apple and the F.T.C. got Amazon.
State attorneys general around the country have also banded together to start separate investigations into Google and Facebook.
The House Judiciary Committee has held multiple public hearings on the subject of the tech companies’ market power as part of its inquiry. It escalated last week when it sent the formal requests to the tech companies and their critics.
In a statement last week, Representative David Cicilline, Democrat of Rhode Island and the chairman of the subcommittee on antitrust, which is leading the Judiciary Committee’s investigation, called the document requests “an important milestone” in the fact-gathering stage.
Separately on Friday, Representative Jerrold Nadler, Democrat of New York, and Mr. Cicilline met with Mr. Zuckerberg, who left the meeting without offering a comment.
Mr. Cicilline said afterward that Mr. Zuckerberg had offered an “ongoing commitment to cooperate in the investigation, and that’s a whole range of things, obviously document requests, requests for information, participation in a number of different ways.”
“And I take him at his word,” he said.