At least 300 visas had been revoked, Secretary of State Marco Rubio confirmed last month, adding that the department would continue to identify student visa holders who it felt had abused its parameters. There are roughly 1.1 million international student visa-holders in the U.S. When international students lose their visas, they are immediately vulnerable to deportation.

Education Secretary Linda McMahon said in an interview Tuesday that universities should do more to vet whether students have any terrorist leanings or “are not necessarily supportive of the United States” before they come to campuses. She cited the increased activity by Rubio in taking away student visas.

The Trump administration has been escalating its crackdown on international students, which began with arrests of several students who participated in pro-Palestine protests. Though the number of visas revoked remains relatively small, recent cases have created widespread fear among foreign students that they could be targeted for unpredictable reasons.

“It seems like they’re going lower and lower on the list of flags in the system to terminate these students’ status,” said Elizabeth Goss, an immigration attorney specializing in higher education, referencing the Immigration and Customs Enforcement database of student visa holders. “It’s totally unprecedented.”

ICE and the State Department didn’t respond to requests for comment.

Dartmouth College doctoral student Xiaotian Liu said in a lawsuit Monday that his visa was revoked on Friday without explanation. He is suing Homeland Security Secretary Kristi Noem and Todd Lyons, the acting director of ICE.

Lui says in the complaint, filed by the American Civil Liberties Union of New Hampshire, that he has never committed a crime or participated in any protests. The Chinese citizen has been studying at Dartmouth since 2023.

“Xiaotian’s dream of finishing his doctoral program and obtaining a Ph.D. at Dartmouth College is now in severe jeopardy,” the lawsuit said, adding that Liu is at risk of being detained or deported. Liu’s lawyer didn’t respond to a request for comment.

The American Council on Education, which represents higher education schools, sent a letter to Rubio and Noem on Friday seeking clarity on why the visas were revoked, saying some people were told to self-deport, with no information on how to appeal the decision.

Immigration attorneys have said, most commonly, the students affected have some sort of arrest or criminal record, including minor charges filed against them that were subsequently dropped. Charges that have resulted in visa revocations include speeding tickets and at least one instance of urinating in public.

“But there are some students where I honestly can’t divine what the reason is for the termination,” said Dan Berger, an attorney in Massachusetts who works with universities in the northeast U.S.

Schools reporting revoked visas varied and were spread from coast-to-coast, from University of Kentucky to Minnesota State University, Mankato, to University of Massachusetts Boston. The move is hitting students from countries across the globe. Undergraduates, graduate students and even those working in the U.S. after graduation on their visas have been targeted.

Visas of seven students at Ohio State University were revoked, according to the school. “The students, their attorneys and Ohio State are considering next steps,” an Ohio State spokesman said.

Across the University of California system, at least 44 visas were revoked from students and recent graduates. At UC San Diego, one student was detained at the border and deported to their home country, the school said, but didn’t provide additional details.

The Trump administration is also investigating 60 schools for alleged antisemitism during pro-Palestinan demonstrations and has been targeting international students who were involved in the protests.

Last month, for example, federal authorities detained Columbia student Mahmoud Khalil, a green-card holder, after he helped lead pro-Palestinian demonstrations.

Bernie Burrola, who works with schools on global engagement as a vice president of the Association of Public and Land-Grant Universities, said the visa revocations have led to concern among international students, unsure if they’ll be targeted next.

“Some are worried, is it a social-media post I made? Is it because I may or may not have been near a protest?” Burrola said. “That is the big fear, just not knowing.”

Write to Joseph Pisani at joseph.pisani@wsj.com, Michelle Hackman at michelle.hackman@wsj.com and Sara Randazzo at sara.randazzo@wsj.com