Sen. Amy Klobuchar (D-Minn.) sent a letter on Thursday to the head of Live Nation Entertainment, accusing the company of abusing its market positions and violating a consent decree amid widespread criticism of Ticketmaster as fans struggle to purchase tickets for an upcoming Taylor Swift tour.

Klobuchar, who chairs the competition, antitrust and consumer rights subpanel of the Senate Judiciary Committee, said Live Nation Entertainment, the result of a merger between Live Nation and Ticketmaster, holds power in the ticket market that “insulates it from the competitive pressures that typically push companies to innovate and improve their services.”

“That can result in dramatic service failures, where consumers are the ones that pay the price,” the senator wrote.

Klobuchar noted Live Nation Entertainment is beholden to an antitrust decree that prevents it from abusing its position in the market. The decree was entered into after the 2010 merger between venue-hosting company Live Nation and ticket-sales business Ticketmaster.

The former presidential candidate requested information about any complaints of noncompliance with that decree, investments the company has made and more broadly about how ticket sales work.

Klobuchar’s criticism of Live Nation Entertainment joins that of Democratic Reps. Alexandria Ocasio-Cortez (N.Y.) and Bill Pascrell (N.J.), who have renewed calls for the company to be broken up following the Swift ticket fiasco.

During a presale event for an upcoming tour, Swift fans have reported a number of issues with the Ticketmaster site, including the website crashing or freezing.

Tennessee’s attorney general has also launched an antitrust investigation into Live Nation Entertainment, noting they dominate 70 percent of the live music industry.

In a Tuesday update,Ticketmaster said there was a “historically unprecedented demand” for the Swift tour and that it was working to clear queues and backlogs as quickly as possible.

The company said hundreds of thousands of tickets have been sold in the pre-sale.