Secretary of State Marco Rubio boasted Thursday that at least 300 student visas have been revoked since President Donald Trump took office and that they’re “looking every day” for more.

“It might be more than 300 at this point. We do it every day. Every time I find one of these lunatics, I take away their visa,” he said at a press conference in Guyana when asked about the number of visas revoked in relation to student protests.

“We gave you a visa to come and study and get a degree, not to become a social activist that tears up our university campuses,” he said. “So we’ll revoke your visa, and once your visa is revoked, you’re in the country illegally and you have to leave.”

The Trump administration has targeted students who participated in anti-Israel demonstrations on college campuses last year, notably at Columbia University where a campus building was briefly taken over.

Columbia last week agreed to implement a number of policy changes, including to its disciplinary, protest and mask rules, after Trump threatened to revoke all of its federal funding if it didn’t make major changes to how it handles student protests.

Among the latest detentions is a Tufts University graduate student from Turkey, who was seen on Tuesday being detained on the streets of Boston by U.S. immigration officials wearing plain clothes and masks. Rumeysa Ozturk, who was in the U.S. on an F1 visa, had co-authored an op-ed last year that urged Tufts’ president to “acknowledge the Palestinian genocide” and divest from companies with ties to Israel.

Her legal team called her detainment by the Department of Human Services unlawful, in a statement Thursday.

“We should all be horrified at the way DHS abducted Rumeysa in broad daylight. No person, regardless of their citizenship status, should be targeted over their views, especially in support of human rights,” said a spokesperson with Khanbabai Immigration Law.

“Rumeysa has not been accused of committing any crime and DHS has not produced any evidence that she was engaged in any unlawful activities. Meanwhile, there is plenty of evidence of U.S. supplied bombs being dropped on Gaza killing over 1,000 people, including over 250 children in the last week. It appears the only thing Rumeysa is being targeted for is her right to free speech.”

Rubio stood by Ozturk’s visa being revoked when asked about her detention on Thursday.

“If you apply for a visa to enter the United States and be a student, and you tell us that the reason why you’re coming to the United States is not just because you want to write op-eds, but because you want to participate in movements that are involved in doing things like vandalizing universities, harassing students, taking over buildings, creating a ruckus, we’re not going to give you a visa. If you lie to us and get a visa and then enter the United States, and with that visa, participate in that sort of activity, we’re going to take away your visa,” he said. “We’re looking every day for these lunatics that are tearing things up and, by the way, we’re looking for gang members as well.”