It is not immediately clear why students’ visas were terminated. Some schools said the federal government had not notified them of their students’ change of status, but rather learned about it when reviewing records.

MEDFORD, Mass. — A Tufts University graduate student is in federal custody, detained by federal authorities outside of an off-campus apartment building in Somerville Tuesday night. Rumeysa Ozturk is petitioning the US District Court for the District of Massachusetts for a writ of habeas corpus.

Students and other community members at UMass Amherst, UMass Boston, and Harvard University had their visas revoked, school leaders said.