Several streets around the University of California, Berkeley, were closed off Thursday with concrete and plastic barriers ahead of an evening appearance by a conservative commentator — the latest polarizing event to raise concerns of violence on the famously liberal campus.

Authorities sealed off Sproul Plaza — the central hub of the campus — and created a perimeter around several buildings, including the site where Ben Shapiro, a former editor of Breitbart News, was set to speak to a sold-out audience of 1,000 people.

Shapiro was invited to speak by campus Republicans, who say the liberal university stifles the voice of conservative speakers.

The city and campus have become a flashpoint this year for the country’s political divisions, drawing extremist groups from the left and right.

“We can’t turn a blind eye to reality and to what we’ve learned from recent events on this campus and in this city and around the country,” UC Berkeley spokesman Dan Mogulof said.

He said the school is committed to ensuring the safety of students and people attending the event, and to making it successful.

There will be several checkpoints outside the auditorium where the speech is planned, and officers will be looking to confiscate banned items such as shields, masks, bandanas, poles and torches, UC Berkeley Police Chief Margo Bennett said.

For the first time in two decades, city officers were authorized by the City Council to use pepper spray to control violence.

University police do not intend to use pepper spray but “that’s not saying we won’t if circumstances call for them,” Bennett said.

City Police Chief Andrew Greenwood said officers would make “very strong, rapid arrests” of protesters wielding weapons and wearing masks.

Four political demonstrations have turned violent in Berkeley since February, prompting officers to come up with new strategies to control rowdy and sometimes dangerous crowds.

“We have seen extremists on the left and right in our city,” said Berkeley Mayor Jesse Arreguin, a Democrat who backed the police request to use pepper spray. “We need to make sure violence is not allowed.”

The Berkeley College Republicans invited right-wing provocateur Milo Yiannopoulos to speak last February, but the event was abruptly canceled when masked left-wing anarchists rioted outside the event to shut it down.

Police and UC Berkeley officials were criticized at the time for giving demonstrators wide latitude and standing aside as the anarchists hurled Molotov cocktails at officers and caused $100,000 worth of damage.

Tighter security measures were expected to disrupt campus life Thursday and later this month, when Yiannopoulos says he plans to hold a “Free Speech Week” on campus that features conservative commentator Ann Coulter and Steve Bannon, ex-chief strategist for President Donald Trump who has returned to Breitbart News.

Campus officials say that event is not yet confirmed.

Sociology professor Michael Burawoy, who is chairman of the Berkeley Faculty Association, said frustration is growing over the disruptions.

“We bring them on campus and allow them to speak and we encourage both right- and left-wing groups” to hold potentially violent protests, he said. “If we exclude them, they say Berkeley doesn’t believe in free speech. It’s a lose-lose situation.”

(AP)