The U.S. House Judiciary Committee this week sent letters to Apple, Alphabet, Amazon and Facebook asking whether their CEOs plan to participate in a series of antitrust hearings slated for July.
With the correspondence, antitrust investigators are pressing executives to testify on their own accord as part of a probe into the business dealings of Silicon Valley tech giants, Axios reports.
The letters raise the specter of potential subpoenas for testimony and document production in cases of noncompliance, the report said. Lawmakers have for months urged executives to testify on behalf of their respective companies as part of a review process that could inform changes to U.S. antitrust law.
"These are documents that are essential to complete our ongoing, bipartisan investigation of the digital marketplace," subcommittee chairman David Cicilline said in a statement. "This is the appropriate process to secure their production."
Cicilline and the House Antitrust Subcommittee announced a bipartisan investigation into "platform gatekeepers" and "dominant" tech firms last year. At the time, specific companies were not mentioned by name, but it was later revealed that the probe targets Apple, Alphabet, Amazon and Facebook.
A similar letter requesting relevant documentation was furnished to companies in September. Apple's Cook was personally asked to provide evidence relating to its App Store business, so-called "Sherlocking" of third-party apps and systemic removal of parental control apps, among other topics.
The companies began to submit documents related to the probe in October, though the process is far from complete.
Augmenting the government review is testimony from third-party companies that allege subjugation by big tech entities. Tile, for example, spoke out against Apple's widely rumored "AirTags" object tracking solution last September.
Tile claims Apple took action against the smaller firm by stopping sale of its products in Apple Stores and crippling location tracking functionality in iOS. Apple also poached a Tile engineer as "AirTags" rumors mounted, suggesting the iPhone maker is readying a competing device.
Other firms, like Luna Display, argue Apple Sherlocked, or adopted, features and software capabilities introduced by third-party developers for integration in iOS and other first-party operating systems.
Music streaming powerhouse Spotify, a regular critic of Apple's App Store policies, was also asked for input on the tech giant's business structure. Spotify founder Daniel Ek previously said Apple "gives themselves unfair advantages at every turn," noting App Store regulations like purchase and subscription fees.
The House Judiciary Committee investigation is one of a handful of government probes into tech companies and their business operations. The U.S. Justice Department, the Federal Trade Commission and state attorneys general are looking into claims of monopolization, price fixing, anticompetitive practices and more.