US Secretary of State Marco Rubio is pushing to investigate whether Harvard University violated federal sanctions, The New York Times reported on Wednesday, citing people familiar with the matter and documents reviewed by the newspaper.

Rubio is pushing to investigate if Harvard violated sanctions by collaborating on a health insurance conference in China that may have included officials blacklisted by the United States, the paper said.

The university has been conducting an internal review into the involvement of the Chinese state-run group Xinjiang Production and Construction Corps at the conference, the paper added.

Rubio signed off on a recommendation to the Treasury Department last month to open an investigation, the report said.

Reuters could not immediately confirm the report.

A treasury department spokesman said the agency takes “any allegations of sanctions violations extremely seriously” but declined to comment on possible or pending investigations. A State Department spokesperson also declined to comment.

A Harvard spokesman declined to comment to The New York Times.

Harvard University did not immediately respond to a Reuters request for comment.

The Trump administration has launched a multi-pronged attack on the nation’s oldest and wealthiest university, freezing billions of dollars in grants and other funding and proposing to end its tax-exempt status, prompting a series of legal challenges.