In the span of a week, a hush has descended on higher education in the United States.

International students and faculty have watched the growing crackdown on pro-Palestinian protesters at Columbia University with apprehension. Some say they are familiar with government crackdowns but never expected them on American college campuses.

The elite New York City university has been the focus of the Trump administration’s effort to deport foreigners who took part in pro-Palestinian demonstrations at colleges last year.

Federal immigration agents have arrested two foreigners — one of them a student — who protested last year at Columbia. They’ve revoked the visa of another student, who fled the U.S. this week. Department of Homeland Security agents also searched the on-campus residences of two Columbia students on Thursday but did not make any arrests there.

GOP officials have warned it’s just the beginning, saying more student visas are expected to be revoked in the coming days.

Columbia’s Graduate School of Journalism issued a statement reporting “an alarming chill” among its foreign students in the past week.

“Many of our international students have felt afraid to come to classes and to events on campus,” said the statement signed by “The Faculty of Columbia Journalism School.”

International students and faculty across the U.S. say they feel afraid to voice opinions or stand out on campus for fear of getting kicked out of the country.

“Green-card-holding faculty members involved in any kind of advocacy that might be construed as not welcome by the Trump administration are absolutely terrified of the implications for their immigration status,” said Veena Dubal, a law professor at the University of California, Irvine.

Dubal, who is also general counsel for the American Association of University Professors, says some international faculty are now shying away from discourse, debate, scholarly research and publishing articles in peer-reviewed journals.