Sen. Elizabeth Warren (D-MA) and Rep. Alexandria Ocasio-Cortez (D-NY) want to know more about “potentially illegal activity” at Sears when Treasury Secretary Steven Mnuchin was a member of its board.

Warren and Ocasio-Cortez sent Mnuchin a letter Thursday saying they were “deeply concerned” about what happened at Sears before it went bankrupt last fall.

The two lawmakers “also asked Mnuchin whether he has been involved in any discussions about Sears’ pension plans as a board member of the Pension Benefit Guaranty Corporation, the federal agency that oversees private pension plans,” reports Politico.

Sears filed a lawsuit last month against its former CEO, Edward Lampert — a friend and former college roommate of Mnuchin — “alleging that board members helped Lampert and his hedge fund strip more than $2 billion from the company,” Politico says. Mnuchin is named in the suit, along with several others.

Warren and Ocasio-Cortez released a video to explain the reasons for their concern.

“Mr. Mnuchin is President Trump’s Treasury secretary, and he is a walking example of what happens when rich and powerful people put other rich and powerful people into power,” Ocasio-Cortez said in the video.

In its lawsuit, Sears says that “Lampert caused more than $2 billion of assets to be transferred to himself and Sears’ other shareholders and beyond the reach of Sears’ creditors.”

Politico says a Treasury spokesperson did not respond to its request for comment.