Developers of iOS apps have been interviewed by investigators working for the US Justice Department about Apple's App Store, as part of an antitrust probe into major tech companies and their control over digital marketplaces, and whether they are competing fairly.

Announced in July 2019, the Justice Department probe aims to examine the level of control companies the size of Apple has over the market at large, as both operators and participants. While open, the probe has progressed relatively quietly, with few public signs of progress at this stage, though it seems the agency is now talking to firms potentially affected by antitrust issues.

Speaking to Reuters, Mocicip chief developer Suren Ramasubbu claims he was interviewed by an investigator in November over the matter, specifically about how Apple interacted with the company. A parental control app, Mobicip was temporarily removed from the App Store over failing to meet requirements set by Apple, Ramasubbu told investigators.

The investigators are continuing to talk to others, as a report source familiar with the probe said a small number of developers were being contacted. It is believed to be the first indication that the investigation is looking into Apple's App Store practices.

Apple did not comment to the report, but referred to a website statement about how the App Store aims to hold apps "to a high standard for privacy, security, and content."

The probe is a review to assess "the widespread concerns that consumers, businesses, and entrepreneurs have expressed about search, social media, and some retail services online," the DoJ said at its announcement. Its Antitrust Division was confirmed as "conferring with and seeking information from the public, including industry participants who have direct insight into competition in online platforms, as well as others."

"Without the discipline of meaningful market-based competition, digital platforms may act in ways that are not responsive to consumer demands," said Assistant Attorney General Makan Delrahim of the Antitrust Division at the time. "The Department's antitrust review will explore these important issues."

These markets include the impacts on fields such as retail, social media, and search, with the App Store classifying under the retail category. The review does not currently have any fixed goals, outside of discovering if there are antitrust problems to at all, with a view to possible prosecution for law violation.