A Senate committee chaired by Sen. Richard Blumenthal has issued subpoenas to Live Nation and Ticketmaster, related to ticket pricing, fees and resale practices.

"We are resorting to the subpoena now because voluntary compliance has been totally inadequate, what they are hiding and why we don't know at this point, but we are aiming to get documents that the subcommittee needs and are entitled to have," said Sen. Blumenthal. 

The investigation started after fans complained that they were unable to buy tickets to the biggest tours of the year, including Taylor Swift and Bruce Springsteen tours.