Dallas-area international students are struggling to navigate why they were told to leave the country immediately after visas were suddenly revoked by federal officials, lawyers working with some of them said.

Students from University of North Texas, UT-Dallas, Texas A&M, UT-Rio Grande, Texas Women’s University, Texas Tech and other schools have been affected.

U.S. immigration authorities have revoked the visas of roughly 90 international students at several Texas universities. The big picture: The Trump administration has revoked the visas of nearly 400 international students across the country in the last three weeks,

We are not aware of the details of the revocations or the reasons for them, but we understand these actions continue to take place at other institutions across the country," Harvard said in a post Thursday.

"We are deeply troubled by the escalation of immigration enforcement activity toward our international students."

The university was not notified and only learned of the changes by proactively checking a government database.

An increasing number of student deportation threats involve the revocation of visas based on relatively minor offenses like years-old misdemeanors, according to immigration attorneys, or sometimes no reason at all.

Hundreds of foreign students across the US have had their visas revoked suddenly and without explanation, lawyers say.