The United States Department of Justice (DOJ) has reportedly launched an antitrust investigation into Live Nation Entertainment-owned Ticketmaster, following the cancellation of last week’s public ticket on-sale for Taylor Swift’s tour.

According to the New York Times, the investigation, which has not been officially announced, is focused on whether the ticketing giant used anti-competitive practices and unfairly leveraged its influence in the ticketing market.

Last week’s ticket onsale was cancelled after “extraordinarily high demands on ticketing systems and insufficient remaining ticket inventory to meet that demand,” Live Nation said. It said millions of fans had registered in advance as “verified fans” with the aim of attempting to buy tickets for Swift’s 52-city US tour during the pre-sale period.

The report said that prior to last week, investigators with the DOJ’s antitrust division have been contacting music venues and other companies in the ticketing industry to ask about Live Nation’s business practices.

Live Nation issued a statement that said, “As we have stated many times in the past, Live Nation takes its responsibilities under the antitrust laws seriously and does not engage in behaviours that could justify antitrust litigation, let alone orders that would require it to alter fundamental business practices.”