At least 10 universities, including Ivy Leagues MIT, Harvard and Columbia, have issued notices to students|Scarlet Sappho|CC BY-SA 2.0

Donald Trump has vowed to crack down on illegal and legal immigration, prompting top universities to advise their international students to be back in the country before the January 20 presidential inauguration.

At least 10 universities, including Ivy League MIT, Harvard, Columbia, University of Southern California, Brown University, and University of Pennsylvania, have issued notices to students stating that the new administration may issue executive orders impacting visa processes and travel to America.

Cornell University has cautioned its international students that a travel ban targeting Kyrgyzstan, Nigeria, Myanmar, Sudan, Tanzania, Iran, Libya, North Korea, Syria, Venezuela, Yemen, Somalia, China, and India will likely go into effect after the Trump inauguration.

According to the nonprofit NAFSA, nearly 1.1 million foreign students are studying in the US, and their tuition contributes $43.8 billion to the economy. During the last academic year, NYU had the most foreign students—over 27,000.

Some students have altered their flights to return early from winter break, while several are canceling plans to travel outside the US once Trump takes office.