According to sources, CMA officials raided the offices in August and seized information about the companies' dealings with popular ticket touts, who buy up tickets for popular events with the intention of selling them on with a high mark-up. The watchdog had earlier issued four ticket resale companies -- including GetMeIn and Seatwave -- with an "information notice" asking for information on their relationships with major resellers and the money they've earnt from ticket sales.

GetMeIn and Seatwave handed over what was asked of them, but eBay-owned StubHub and Swiss-based Viagogo did not comply.

It's believed that officials targeted data relating to StubHub's "top seller" programme, which provides its biggest resellers -- who sell more than $250,000 worth of tickets a year -- with exclusive discounts on fees and a dedicated platform that allows them to better manage their listings.

StubHub said in a statement: "We understand the CMA investigation is ongoing and therefore await the outcome of this."