At least 147 international students were abruptly stripped of their ability to stay in the United States in recent days, according to universities and media reports, sowing fear among students and confusion at schools scrambling to help students facing detention and possible deportation.

The moves targeted students at a wide range of universities, from private institutions like Harvard and Stanford to public ones like the University of Texas at Austin and Minnesota State University-Mankato. The University of California had dozens of cases reported across its campuses.

Several immigration lawyers told The New York Times that they began receiving frantic emails and calls late last week from students who had been notified by the State Department or their universities that their visas or statuses had been terminated without clear justifications.

Criminal convictions have always put students at risk of losing their statuses, but traffic infractions and participation in political actions have rarely been cited as grounds.

In some cases, immigration officers have arrested international students related to their involvement in pro-Palestinian causes. In other cases, students had committed legal infractions, such as driving over the speed limit or while intoxicated, often years ago, several immigration lawyers said in interviews.

But lawyers said the Trump administration had often given no reason at all, leaving them to guess why students were targeted.

“This upends all usual practice by the government,” said Miriam Feldblum, chief executive of the Presidents’ Alliance on Higher Education and Immigration, which represents more than 570 public and private colleges and universities across the country. “They are terminating students’ statuses in a way they have never done before and with virtually no explanation and little recourse to correct or appeal by either the institution or the students.”

Late last month, Marco Rubio, the secretary of state, ordered diplomats to scour the social media postings of some visa applicants to keep away from the country those suspected of criticizing the United States and Israel.

The State Department and the Department of Homeland Security did not immediately respond to messages seeking comment.

The recent moves add more anxiety to an already precarious environment for international students and scholars in the United States. Advocates for international education worry that such moves will chill the ability of U.S. schools to attract foreign students.

Last month, Mahmoud Khalil, a recent Columbia University graduate student who was involved in pro-Palestinian activism during campus protests last year, was arrested at his apartment and sent to Louisiana for possible deportation, despite being a permanent resident. Shortly after, Rumeysa Ozturk, a Tufts University student from Turkey, was detained by masked agents from U.S. Immigration and Customs Enforcement, while she was on the way to meet friends. Ms. Ozturk, who had written a pro-Palestinian opinion essay, was also taken to Louisiana.

The moves aimed at international students fit with the Trump administration’s broader policy agenda of reducing the number of immigrants, both legal and undocumented, and of forcing universities to crack down on what the president says is rampant antisemitism on campuses.

The United States issued more than 400,000 visas to students in 2024.

Some of the students targeted recently had committed offenses like speeding or driving while intoxicated, the lawyers said. They said that such offenses did not ordinarily rise to deportation.

Without a visa an international student becomes undocumented, and must leave the United States or risk being detained and placed in deportation proceedings. Several attorneys said that they had clients who had opted to leave the country out of fear that they could be arrested by agents from ICE, the Homeland Security agency charged with carrying out Mr. Trump’s pledge of mass deportations.

Some of the affected students are graduate students who have doctoral dissertations that they are supposed to defend next month. Others are undergraduates. Still others have completed their studies and have been working in the United States, under a special program that allows recent international graduates to remain in the country for up to three years if employed.

“This is totally unprecedented,” said Fuji Whittenburg, an immigration lawyer in Calabasas, Calif., who has been practicing law for 20 years. “I have never seen anything close to this.”

She added, “A brush with law enforcement that didn’t necessarily result in an arrest or a conviction is all it took.”

Ms. Whittenburg said that one of her clients was an Indian national who got a DUI when he was studying in the United States more than a decade ago. When he applied for a second student visa more recently, he disclosed the charge to U.S. consular authorities in his home country. They ultimately granted him the visa to pursue further studies in the United States.

Harvard advised international students last week during a webinar to reconsider traveling abroad, according to The Harvard Crimson, the student newspaper. The staff also warned students that pro-Palestinian speech could be risky.

During the webinar, Jason Corral, an attorney, said there seemed to be a change from President Trump’s first term, according to The Crimson. “The difference is we have seen situations where it seems as though people’s visas are being revoked simply based on their speech or protests,” he said.

In an alert, a coalition of national student media organizations urged student media last week to “minimize harm,” citing threats to student speech.

On Monday a letter sent to Michael Drake, the president of the University of California, and others by the Council of University of California Faculty Association said the university should help students who had been targeted, arguing it had a “moral obligation” to protect students and scholars’ legal rights.

The letter, which was co-signed by the University Council AFT, a teaching faculty and librarians union, called on the university to allow deported or detained students to continue their programs remotely, to continue providing stipends, salaries and fellowships and to help students in the courts.

Several students have sued the government to challenge their terminations, and lawsuits are expected to pile up.

Stacy Tolchin, an immigration lawyer in Pasadena, Calif., filed two suits in federal court in Los Angeles on Saturday, and said that she would be filing more this week.

In one case, the American Civil Liberties Union is representing a Chinese doctoral student at Dartmouth College who has been studying computer science. According to a complaint filed on April 4, the student, Xiaotian Liu, had not committed any crimes or participated in any protests.

The college told the student in an email that this was “not standard or normal procedure,” according to the lawsuit, which was filed in federal court in New Hampshire.

“Xiaotian’s dream of finishing his doctoral program and obtaining a Ph.D. at Dartmouth College is now in severe jeopardy,” the lawsuit said.