The US State Department is screening all visa holders affiliated with Harvard University, not just students, three senior State Department officials told CNN.
The officials did not say why such a check was being conducted.
The recent moves come amid measures by the Trump administration that could discourage foreign students from attending U.S. universities.
This week, the State Department announced several other steps aimed at students who want to come to the US. The department has suspended all new student and exchange visas as it prepares to expand social media vetting of applicants. It is currently unclear exactly what the expanded social media vetting will include.
The move is a notable escalation of the Trump administration’s feud with the Ivy League university.
The administration had previously tried to stop Harvard from enrolling international students, but that attempt was stopped by a federal court. Harvard argued that revoking its certificate in undergraduate and exchange programmes was “clear retaliation” for refusing the government’s demands.