WASHINGTON — Colleges around the country are reporting some of their international students’ visas are being revoked unexpectedly, expressing alarm over what appears to be a new level of government scrutiny.

Visas can be canceled for a number of reasons, but college leaders say the government has been quietly terminating students’ legal residency status with little notice to students or schools. That marks a shift from past practice and leaves students vulnerable to detention and deportation.

The list of colleges that have discovered students have had their legal status terminated includes Harvard, Stanford, Michigan, UCLA and Ohio State University.

The Trump administration has targeted students who had been involved with pro-Palestinian activism or speech, with a few high-profile detentions of students including Mahmoud Khalil, a green card holder who was a leader of protests at Columbia University.

But more schools are seeing visas stripped from students with no known connection to protests. In some cases, past infractions such as traffic violations have been cited. Some colleges say the reasons remain unclear to them — and they are seeking answers.

“What you’re seeing happening with international students is really a piece of the much greater scrutiny that the Trump administration is bringing to bear on immigrants of all different categories,” said Michelle Mittelstadt, director of public affairs at the Migration Policy Institute.

Many college officials and students have only found out about the changes when they have checked a federal database and seen changes to an individual’s immigration status.

How Do Student Visas Work?

Students in other countries must meet a series of requirements to obtain a student visa, usually an F-1. After gaining admission to a school in the U.S., students go through an application and interview process at a U.S. embassy or consulate abroad.

Students on an F-1 visa must show they have enough financial support for their course of study in the U.S. They have to remain in good standing with their academic program and are generally limited in their ability to work off-campus during their academic program.

Entry visas are managed by the State Department. Once they’re in the U.S., international students’ legal status is overseen by the Student and Exchange Visitor Program under the Department of Homeland Security.

Leaders at many colleges learned the legal status of some of their international students had been terminated when they checked a database managed by Homeland Security. In the past, college officials say, visas typically were revoked after schools updated the government when students fell out of status.

Students Told to Leave the Country

Historically, students who had their visas revoked were allowed to keep their legal residency status and complete their studies.

The lack of a valid visa only limited their ability to leave the U.S. and return, something they could reapply for with the State Department. But if a student has lost residency status, they must leave immediately or risk detention by immigration authorities.

Higher education leaders worry the arrests and revocations could have a chilling effect on international education in the United States.

The lack of clarity of what is leading to revocations can create a sense of fear among students, said Sarah Spreitzer, vice president of government relations at the American Council on Education.

“The very public actions that are being taken by ICE and the Department of Homeland Security around some of these students, where they are removing these students from their homes or from their streets, that’s not usually done unless there is a security issue when a student visa is revoked,” she said. “The threat of this very quick removal is something that’s new.”

Colleges Trying to Reassure Students

In messages to their campuses, colleges have said they are asking the federal government for answers on what led to the terminations. Others have re-emphasized travel precautions to students, recommending they carry their passport and other immigration documents with them.

College leaders spoke of a growing sense of uncertainty and anxiety.

“These are unprecedented times, and our normal guiding principles for living in a democratic society are being challenged,” University of Massachusetts Boston Chancellor Marcelo Suárez-Orozco wrote in an email. “With the rate and depth of changes occurring, we must be thoughtful in how we best prepare, protect, and respond.”

Suárez-Orozco said the legal residency status had been canceled for two students and “five other members of our university community including recent graduates participating in training programs.”