Police arrested more than 20 people near the Hofstra University campus where the presidential debate is being held, officials said Monday night.

Twenty-three people were charged with disorderly conduct and obstructing governmental administration on Earle Ovington Boulevard at 6:50 p.m., Nassau Det. Lt. Richard LeBrun said.

About 10 minutes earlier, one person was arrested for obstructing the roadway on Hempstead Turnpike, LeBrun said. The person was trying to get over a barricade in the middle of the broad roadway, he said.

It was not immediately clear if anyone was injured.

The arrests occurred near the area set aside for demonstrators on a portion of the campus on the south side of the turnpike.

That is well away from the David S. Mack Sports and Exhibition Complex, where the first presidential debate between Democratic nominee Hillary Clinton and Republican candidate Donald Trump began shortly after 9 p.m. The complex is located on the part of campus north of the turnpike.

Protesters had arrived at designated areas around Hofstra on Monday afternoon. At one point, more than 100 Black Lives Matter protesters who had been chanting “No justice, no peace, no racist police” merged with another demonstration by several dozen peace activists and environmentalists.

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Hofstra professor Michael D’Innocenzo told the crowd that their protest sought “to raise issues we think the candidates should be addressing,” but aren’t — among those, excessive military spending, aggressive foreign policy, neglected women’s rights, better funding for education, police brutality and needed immigration reform.

Margaret Melkonian, a Long Island peace activist, said the group — in a so-called “free speech zone” south of the turnpike — was there to call for a more peaceful world, while “the war candidates are on the other side.”

“Tell me what democracy looks like!” chanted one leader. The crowd chanted back: “This is what democracy looks like!”

Natasha Rappazzo, of the Hofstra Campus Feminist Collective, said the protest was not about Democrats or Republicans but about issues.

“A feminist president doesn’t just mean a female president,” Rappazzo said. “We need someone that is going to speak for the people.”

The protest ended and people left after about an hour.

In a separate demonstration, a group of more than 30 Mexican immigrants — upset that Trump was coming to Hofstra, near their home — came to Hempstead Turnpike to register their displeasure.

They chanted in Spanish: “¡No te queremos! ¡No te queremos!” Or: “We don’t want you!”

“We don’t like Trump. All he’s doing is creating more hatred in the country,” said Jovani Garcia, 33, a construction worker, who said he came to Long Island from Mexico when he was 3 years old.

“He thinks we are all rapists, we are all killers, murderers, and drug dealers and we’re not,” Garcia said, referring to some of Trump’s statements earlier in the campaign. “We’re hardworking people.”

Of Clinton, he said, “at least she’s giving us a chance” and doesn’t propose kicking many immigrants out of the United States.

By the time the debate began, immigrant advocate Osman Canales noted that there weren’t many people in the free speech area as compared with earlier presidential debates held at Hofstra.

“There’s a lot of security with all the street closures and it’s made it harder for people to come,” Canales said.

“These are people who will represent us all, and we should have the right to have them hear our voices,” he said, referring to the candidates.

On Monday afternoon, police escorted Green Party candidate Jill Stein off campus and gave her a ride to her nearby hotel, officials said. Stein had gained credentials to come on campus to do a TV interview, but once that was over, she had to leave, LeBrun said.

“This is not what democracy looks like, but they are being very nice,” said Stein, who added she would come back later for another interview.

Acting Police Commissioner Thomas Krumpter earlier had said Stein would be treated like any other demonstrator and would be arrested if she breached security.

The Nassau Police Department had prepared for large numbers of demonstrators, with Krumpter estimating as many as 10,000 could gather in the special zones before the debate.

By 7 p.m., however, it appeared there were far fewer protesters present. By 9:30 p.m., with the debate under way, between 100 and 200 people were concentrated at the corner of the turnpike and California Avenue.

They included people protesting the Trans-Pacific Partnership global trade agreement, known as TPP; Hasidic Jews opposing a Jewish state; Haitian immigrants against Clinton’s election; and Christian pastors.

Several preached or shouted slogans on megaphones, though few people stopped to listen.

The department had more than 1,000 sworn officers, including “a significant number of undercover officers in plainclothes and suits,” on hand, Krumpter said.

Snipers from the department’s Bureau of Special Operations were on rooftops, and uniformed officers lined Hempstead Turnpike.

“People have the right to exercise free speech and we’ll protect that right — but by the same token, violence won’t be tolerated, trying to breach security won’t be tolerated,” Krumpter said Monday afternoon as he stood on Hempstead Turnpike outside the university’s main entrance.

Krumpter said officers from State Police, NYPD, the Metropolitan Transportation Authority, Suffolk, and Hempstead and Garden City villages also were on hand, as well as the FBI, ATF and Secret Service.

Among the security technology was a helium balloon holding a video camera stationed hundreds of feet in the air above the free-speech zone.

Krumpter said video was fed into the department’s on-site operations center, giving police a bird’s-eye view into the demonstration area.