A Nevada university instructor is furiously back-pedaling after warning that his classroom is not a “safe space” and vowing to turn students in to immigration authorities if he suspects they are in the country illegally.

The controversial comments are one more example of a mounting anti-immigrant rhetoric ignited by the presidential election, but it’s among the most significant to date on an American college campus from a faculty member.

The University of Nevada, Las Vegas launched an investigation after a student revealed a Facebook conversation with math teacher George Buch in which Buch said he would contact officials from Immigration and Customs Enforcement about any undocumented immigrant students.

“No safe spaces in my classes” for such students, read Buch’s post to one of his students, whose parents are Cuban. “I would have to turn you into ICE,” he posted. “I don’t mind diversity ... I mind criminals.”

But after an uproar on campus over the posts, Buch insisted to the student newspaper that he was just kidding.

“I’m extremely sorry for the comments. I know how hurtful they are to many of you,” Buch said in a statement to UNLV’s Rebel Yell. “It was intended to be a joke, although clearly a poor one. I have never, nor will I ever, create a classroom of hate or intolerance. These students and their success mean everything to me, and I’m sorry that I put them in jeopardy.”

The comments were widely denounced by students and faculty members, and some 80 members of the community held a news conference Thursday to address the issue, the Las Vegas Review-Journal reported.

“We particularly take offense when an instructor who’s supposed to create a positive learning environment actually does the opposite by intimidating and scaring our students,” Francisco Morales, state director for the Center for Community Change Action, said at the news conference.

Buch has been a popular instructor on campus and has been ranked highly by students on a website ranking teachers.

His comments have also been supported by some students speaking out against undocumented immigrants.

@UNLVCSUN If they are illegal, then they are illegal. Stop sugar coating it. — DJ Flaccidity (@BlackPeopleGif) December 1, 2016

Barrett Morris, director of UNLV’s Office of Compliance, said his office would investigate complaints of “these allegations of intimidation/discrimination against Professor Buch and will follow up with you when we have appropriately vetted these concerns.”

UNLV President Len Jessup is one of hundreds of American university presidents who signed a letter supporting the Deferred Action for Childhood Arrivals (DACA) program. DACA allows undocumented immigrants who entered the country before their 16th birthday to obtain a work permit and protection from deportation.

CORRECTION: This article originally misstated the first name of the UNLV teacher who made the comments on Facebook.