Yale University in New Haven, Connecticut, is under federal investigation for its employment of people holding J-1 visas. Credit: Joe Buglewicz/Bloomberg/Getty

A US investigation into nine universities’ employment of international researchers is prompting concerns among academics at the campuses.

The investigation is focused on the universities’ use of J-1 visas , the main visa used by international postdoctoral researchers . The probe’s purpose is to reduce “visa fraud”, according to vice-president JD Vance.

“They’re using these visas way too much,” Vance said when announcing the investigation on 8 October.…