The U.S. Department of Justice reportedly moved closer to filing an antitrust lawsuit against Apple. The DOJ has investigated the iPhone-maker over the past several years and begun to actually write a potential suit.

The government agency has looked into many aspects of Apple’s business and there’s no clear word on whether the complaint will be about the App Store or something else.

U.S. lawmakers want to talk to the CEOs of the biggest tech firms. And the heads of Amazon, Facebook and Google said they‘re willing to testify in the House of Representatives’s probe into antitrust activities. Apple, on the other hand, reportedly told Congress that it’s willing to send a senior executive, but stopped short of promising that would be CEO Tim Cook.

The U.S. Justice Department is reaching out to parental app control companies that may have been affected by Apple’s allegedly anti-competitive App Store practices.

Reuters reported this morning that Suren Ramasubbu, the chief executive developer of Mobicip, was interviewed by US investigators. Mobicip, which allows parents to control what kids access on their iPhones, was kicked out of the App Store last year because it failed to meet new app requirements.