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.

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.

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

The recent graduates whose visas were revoked were on post-completion OPT status, according to university officials, which allows them to work in the US for up to one year after they graduate.