House Democrats are investigating StubHub CEO Eric Baker over revelations that the executive is also operating a separate ticket broker service on the platform, citing concerns that Baker may have “engaged in market manipulation and self-dealing at the expense of consumers.”

In a letter addressed to Baker on Friday, Rep. Robert Garcia, Ranking Member on the U.S. House Committee on Oversight and Government Reform, told the executive that “Oversight Democrats are investigating whether you have manipulated markets for your own benefit, while Americans are left paying higher costs in an unfair system.”

“Reports suggest that you have financed and profited from the very scalpers that are locking fans out of affordable ticket sales in the first place, and that you are further ripping off consumers and smaller sellers by giving yourself preferential treatment on the StubHub platform,” Garcia wrote.

Along with serving as CEO of StubHub, one of the live music business’s largest ticket resale platforms, Baker also serves as a co-owner and managing director of Andro Capital, a separate company that lists and resells tickets of its own on the platform. StubHub had disclosed Baker’s relationship with Andro in the company’s S-1 filing ahead of its IPO last year, though it had only come under scrutiny after an investigative report from CBC news in recent weeks.