Amid heightened tensions over a national crackdown on illegal immigration, an angry crowd surrounded the scene of a car crash involving a federal agent in Westbury on Tuesday afternoon after an appearance by Homeland Security agents in the area.

Close to 100 people converged a block from the Park Avenue Elementary School, shouting at police and federal agents to get out of their community. Some of the agents wore clothing with HSI insignia, for Homeland Security Investigations, the federal department that oversees the U.S. Immigration and Customs Enforcement agency. Unmarked vehicles with HSI agents were seen nearby.

A heavy presence of police vehicles, ambulances and mounted officers soon descended on the scene. After about an hour, the crowd dispersed, without incident, and police left as well.

The clash erupted after an unmarked silver Nissan driven by a federal agent was involved in a crash at about 1:30 p.m. at the corner of Prospect Avenue and Sylvester Street in New Cassel, Nassau County police said.

The agent, who suffered minor injuries, was taken to the hospital by authorities in a black SUV, police said. Her vehicle was later towed away by a Nassau police emergency services unit van.

The driver of a black Nissan pickup also involved in the accident suffered minor injuries, police said. He was carried off on a stretcher and then driven to the hospital.

Authorities did not say what the agents were doing in Westbury or if their work involved the school. But many residents feared the agents' appearance was related to the immigration crackdown, despite later assurances by police that they were not from ICE. The agents had been parked in cars near the school for hours Tuesday, according to witnesses.

"Those agents were not working for ICE," Det. Lt. Scott Skrynecki of the Nassau County Police Department said at the scene. "They were in town on an unrelated investigation."

"There are no arrests, and there's no threat or problem with safety in the community," Skrynecki said.

The Westbury school district said in a statement that it "has been made aware of reports of suspected ICE officials in our community. However, at no point this week, or any other week, have ICE officials requested entry to any of our district buildings or been on school grounds."

Top officials in the Trump administration have said they want immigration agents to increase arrests nationwide to 3,000 a day. The jump in arrests has led to confrontations in recent days between law enforcement and protesters throughout the country, including in Los Angeles and New York, where demonstrations were held Tuesday.

Hundreds of protesters gathered at Foley Plaza in Manhattan across the street from the federal immigration court on Tuesday evening.

Painter Sam Messer, originally from Syosset now living in Brooklyn, held a black sign with white letters that said "Abolish I.C.E."

"I'm against ICE in the way that it's being used, and the way that it's being actually weaponized, to just pick up anyone and to use it basically as as a tool for fear," he said.

Leah Casteneda, 22, who lives in North Jersey, but is originally from Lima, Peru, said that she joined the protest to show her opposition to the policy of separating families at the Southern border.

"This zero-tolerance policy is not giving immigrants due process," she said.

In Westbury, later Tuesday, a small group of people gathered outside the elementary school during dismissal. 

Carina Hernandez, 45, of Westbury, said federal agents were seen in the neighborhood and community members started shouting at them. Some surrounded the cars of the agents.

"We told them they don't belong in Westbury," Hernandez said.

Hernandez said many in the community feared the agents were targeting immigrants.

"I'm a mom and I'm speaking up with a voice because a lot of people can't talk. They're scared. Thank God I'm legal in this country, but a lot of people are not blessed," Hernandez said.

Jairo Reyes, president of the Westbury PTA Council, also said residents were upset about the appearance of the agents. Arrests of immigrants in the country illegally have ramped up nationwide over the past week, according to immigration advocates.

"It’s worrying for our kids, for our parents," Reyes said. "Most of our parents in the community don’t feel safe to go and drop off their kids" at school.

Federal agents are "not looking for criminals ... they’re looking to target our communities," he said.

Newsday's Janon Fisher contributed to this story.