Stanford University is the latest California school to report that the visas of several students and alumni have been revoked as part of a sweeping crackdown by the Trump administration.

Stanford confirmed in a statement Sunday that the visas of four students and two recent graduates had been revoked.

“The University learned of the revocations during a routine check of the [Student and Exchange Visitor Information System] database,” it said. “Stanford notified the students of the revocations and made external legal assistance available to them.”

Secretary of State Marco Rubio said last month that the State Department has revoked 300 or more students’ visas, seeming to target foreign-born students who participate in political activism. Several high-profile pro-Palestinian scholars have been detained by Immigration and Customs Enforcement.

The visas of more than three dozen students and alumni of California universities have been nullified in the last week. Schools did not provide details, citing privacy concerns.