Lawyers for the DOJ have asked Apple, its customers and competitors questions about how the company maintains its strict control over the iPhone, the report said, citing two people with knowledge of the investigation.

The investigation is very "likely to lead to a lawsuit, though the specifics are still in flux," according to the report.

The DOJ declined to comment, while Apple did not immediately respond to a Reuters request for comment.

(Reporting by Noor Zainab Hussain in Bengaluru and Diane Bartz in WASHINGTON; Editing by Aditya Soni)