Officials at the state and federal level have begun looking into the circumstances surrounding a pre-sale of Taylor Swift concert tickets on Ticketmaster earlier this week. Swift fans swarmed the website on Tuesday, reporting website outages and long waits to buy tickets.

Ticketmaster said Swift’s tour generated unprecedented demand, and the company worked quickly to fix problems. They added an additional pre-sale Wednesday, where ticket buyers reported a similar experience.

“There has been historically unprecedented demand with millions showing up to buy tickets for the TaylorSwiftTix Presale,” Ticketmaster said in a Tuesday tweet. “Hundreds of thousands of tickets have been sold… Thank you for your patience as we continue managing this huge demand.”

The Ticketmaster situation has led to antitrust concerns from state and federal officials. Sen. Amy Klobuchar (D-MN), chair of a Senate subcommittee on antitrust issues, sent a letter to Live Nation Chief Executive Michael Rapino Thursday. She asked him a handful of questions, including how much the company had spent to upgrade technology to handle demand surges and what percentage of high-profile tour tickets were reserved for presales.

“I write to express serious concerns about the state of competition in the ticketing industry and its harmful impact on consumers. Reports about system failures, increasing fees, and complaints of conduct that violate the consent decree Ticketmaster is under suggest that Ticketmaster continues to abuse its market positions,” Klobuchar wrote in the letter about the Taylor Swift ticket situation. “Ticketmaster’s power in the primary ticket market insulates it from the competitive pressures that typically push companies to innovate and improve their services.”

Sen. Klobuchar’s letter came a day after Tennessee Attorney General Jonathan Skrmetti said he is looking into the situation. Some of the shows on Swift’s tour are at Nissan Stadium in Nashville.

“Tennessee Attorney General Jonathan Skrmetti is concerned about consumer complaints related to @Ticketmaster’s pre-sale of @taylorswift13 concert tickets,” Skrmetti’s office announced on Twitter Wednesday night. “He and his Consumer Protection team will use every available tool to ensure that no consumer protection laws were violated.”

Reuters and Axios contributed to this report.