A former lobbyist for an association of for-profit colleges resigned last Friday from the Department of Education, where he had worked for about a month.

As ProPublica reported last week, the Trump administration had hired Taylor Hansen to join the department’s “beachhead” team, a group of temporary hires who do not require approval from the U.S. Senate for their appointments.

On the day Hansen resigned, Sen. Elizabeth Warren, D-Mass., sent a letter to Secretary of Education Betsy DeVos, citing ProPublica’s reporting and requesting more information on Hansen’s role.

“Mr. Hansen’s recent employment history clearly calls into question his impartiality in dealing with higher education issues at the Department of Education, and raises alarming conflicts of interest concerns,” she wrote.

Jim Bradshaw, an education department spokesman, told ProPublica in an email that the department was “grateful for [Hansen’s] contributions.”

“He served ably and without conflict and decided his service had run its course,” said Bradshaw. Hansen did not immediately respond to ProPublica’s request for comment. Bloomberg first reported Hansen’s departure.

Hansen isn’t the only hire from the for-profit college industry to join the Education Department via the beachhead team. The New York Times reported that Robert S. Eitel, a former compliance officer at for-profit college operator Bridgepoint Education Inc., is working at the department. Eitel, a former deputy general counsel at the Education Department from 2006 to 2009, has been a critic of federal regulations on for-profit colleges.

Warren also criticized Eitel’s hiring in her letter to DeVos. She noted that the Consumer Financial Protection Bureau last September ordered Bridgepoint, Eitel’s former employer, to refund $23.5 million to students whom it had deceived into taking out loans that cost more than advertised. Bridgepoint is currently under investigation by the Department of Justice, the Securities and Exchange Commission, and the attorneys general of New York, North Carolina, California and Massachusetts, Warren wrote.

Until July 2016, Hansen worked as a registered lobbyist for the nation’s largest trade group of for-profit colleges, Career Education Colleges and Universities, or CECU. He lobbied to weaken a regulation known as “gainful employment,” which permits the education department to rescind federal funding from schools whose students fail to earn enough to repay their debts.

Just weeks after Hansen was hired by the Education Department, it began scaling back the regulations by delaying the deadline of certain provisions of the gainful employment rule. The move gives colleges three extra months to submit appeals and publish disclosures about the high debt loads of their graduates, while the department reviews the implementation of the rule.

Hansen told ProPublica that he wasn’t working on the gainful employment regulations at the department, but he would not specify his responsibilities. He declined to comment on whether his role raised a potential conflict of interest.

Hansen worked as CECU’s director of legislative and regulatory affairs from December 2013 to July 2016 and was a registered lobbyist for the group for the first half of 2016. Over the past five years, CECU has spent about $3.5 million lobbying on behalf of its more than 600 member institutions, the majority of which are for-profit colleges.

Shortly after his inauguration, Trump relaxed the Obama administration’s restrictions on hiring lobbyists. He issued an ethics order that allowed former lobbyists, such as Hansen, to work for agencies that they recently sought to influence. The policy does preclude former lobbyists from working on any “particular matter” on which they lobbied.

Hansen would have been ineligible to work at the Education Department under the Obama administration’s policies.

Hansen’s father, William Hansen, served in the early 2000s as deputy secretary of the Education Department, where he helped to roll back regulations on for-profit colleges. After leaving the department, William Hansen worked for several years as a lobbyist for Apollo Group Inc., the parent company of for-profit college chain the University of Phoenix.

Ben Miller, the senior director of postsecondary education at the Center for American Progress, said that the lack of transparency around Hansen’s hiring raises concerns about temporary hires at the Education Department.

“His entire tenure shows we need much more information on how the beachhead teams work,” Miller said.