Long Island college and university leaders are advising international students and scholars to postpone travel outside the United States if they are from any of the seven majority-Muslim countries in a 90-day travel ban, as higher education institutions grapple with the impact of President Donald Trump’s executive order.

The order — which affects holders of student and visitor visas from Iran, Iraq, Libya, Somalia, Sudan, Syria and Yemen — brought expressions of dismay from college presidents, who voiced support for their international students and global scholarship, and fueled a campus demonstration Monday at Columbia University and a statement of denunciation endorsed by student government leaders at all 64 State University of New York campuses.

Trump’s order, signed Friday afternoon, also put an indefinite freeze on the entry of refugees from Syria.

Hofstra University officials on Monday said one of their students, a citizen of a country included in the ban, was prevented from boarding his scheduled flight back to the United States over the weekend. The Hempstead university’s spring semester began Monday.

“We are deeply disturbed that this student may be unable to return to continue his studies and are exploring all options. This student is the only one currently enrolled at the university from a nation listed in the travel ban instituted by presidential executive on Jan. 27,” a university statement said. No other details were available.

Hundreds of students and faculty gathered Monday evening on the steps of Columbia’s iconic Low Memorial Library to protest and ask the school to protect international students against immigration authorities.

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“We are here to stand together, Egyptians, Saudis — all the nations who are not part of the ban — to protect our brothers and sisters,” said comparative literature professor Hamid Dabashu, an Iranian who has taught at the university for 28 years.

Graduate journalism student Riham Alkousaa, 26, of Syria, said she worries whether she will be able to complete her degree, for which she received a full scholarship.

“I waited three years to get into the best journalism program in the world, and now I am sad,” she said, holding back tears. “I never thought this would happen here.”

Over the weekend, Stony Brook University doctoral student Vahideh Rasekhi was detained at Kennedy Airport. Rasekhi, of Iran, is earning a Ph.D. in linguistics and is president of the school’s Graduate Student Organization. She had been visiting her family and began her travels back to the United States before the executive order went into effect.

It’s unclear how many students attending local colleges are from the majority-Muslim countries in the ban. College administrators said Monday that students from other nations also have expressed concern about what it could mean for them.

Students who are not citizens or permanent residents of the United States typically enter the United States in nonimmigrant F-1 student or J-1 exchange visitor status.

According to the U.S. Department of Homeland Security’s website, there are 286,408 people with student and exchange visas, which includes principals, spouses and children. That number includes the F-1 and J-1 categories.

During the 2015-16 academic year, the majority of international students studying in the United States were from China, India and Saudi Arabia.

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American colleges and universities that year saw a 7 percent rise in the number of students from one of the seven countries included in the travel ban. New York University and Columbia were among the top hosting schools, according to data compiled by the Institute of International Education, an independent nonprofit organization.

“This is happening to us right here in the state university system,” said Marc Cohen, president of the State University of New York Student Assembly. “We are joining with our partners in the CUNY system — about 1.3 million of us — and asking everyone to call their Congress member and senator to get this thing reversed.”

Cohen and the student government presidents of each school in the SUNY system unanimously approved a statement that said, “We, the elected leaders from across the 64 campuses of the largest system of public colleges and universities in the country, stand united in our shame of this hateful decision.”

After Rasekhi’s release, Stony Brook University President Samuel L. Stanley sent a letter to the 25,700-student campus reinforcing the school’s “unwavering commitment to diversity.” The university will host an information session with legal experts on Wednesday at 1 p.m. in the Wang Center Theater, Stanley said, to address the impact of the executive order and answer questions from international students.

SBU officials said the school has 60 students from Iran, one from Iraq, one from Sudan and two from Yemen; seven faculty members are from Iran.

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NYIT Interim President Rahmat Shoureshi on Monday issued a similar statement, offering immigration and visa counsel and support. The school, which has campuses in Old Westbury and Manhattan, has 1,833 international students, seven of whom are from the countries in the travel ban. The school’s fall enrollment was 9,300.

“We fully support the rights of everyone to pursue their academic and scholarly goals in the U.S. and abroad,” Shoureshi said in a letter to the campus community.

John S. Nader, president of Farmingdale State College, said the school’s data showed no students from one of the seven countries in the executive order. But for weeks, students and faculty have expressed concern about international and immigrant students on campus.

“We are assuring our international students, regardless of where they are from, that we will provide every legal protection,” he said.

With Maria Alvarez