A spokeswoman for the Department of Homeland Security suggested on Saturday that three Democratic members of Congress might face assault charges after a confrontation outside an immigration detention facility in Newark during the arrest of the city’s mayor, even as new details emerged that appeared to contradict the Trump administration’s account of the surrounding events.

The three lawmakers — Representatives Bonnie Watson Coleman, Rob Menendez and LaMonica McIver of New Jersey — were inside the facility on Friday for what they described as a congressional oversight visit, which they have the right to conduct under federal law. The facility, Delaney Hall, received its first detainees last week and is eventually expected to hold as many as 1,000 migrants at a time.

Soon after the legislators left the building on Friday afternoon, Newark’s mayor, Ras J. Baraka, was arrested by the head of Homeland Security Investigations in a brief but volatile clash that involved a team of masked federal agents wearing military fatigues and the three lawmakers. He was then taken to a separate federal Immigration and Customs Enforcement facility in the city and released five hours later.

Precisely what led to Mr. Baraka’s arrest on federal trespassing charges, in a public area outside a facility that is owned by a private prison company, remains unclear. But much of what unfolded was recorded by journalists, as well as by cameras worn by law enforcement officials and videos taken by activists protesting nearby.

Tricia McLaughlin, the Homeland Security spokeswoman, told CNN on Saturday that a body camera video showed “members of Congress assaulting our ICE enforcement officers, including body-slamming a female ICE officer.”

The episode was under investigation, she said, and charges against the three lawmakers were “definitely on the table.”

But videos the Trump administration released to Fox News appeared to be far from conclusive, and accounts of the confrontation from witnesses and the members of Congress differ in significant ways from the government narrative.

On Friday, after Mr. Baraka’s arrest, Ms. Watson Coleman, 80, described being “manhandled” by agents who were attempting to arrest the mayor, who was at the center of a large group of aides and supporters in front of the gates to Delaney Hall.

“There was just consistently, and across the board — especially with the folks in uniform — no respect for who we were and no respect for the mayor,” she said Saturday on MSNBC.

In February, the Trump administration entered into a 15-year, $1 billion contract with GEO Group to turn Delaney Hall into a large detention center as ICE rushed to expand its detention capacity nationwide to meet President Trump’s mass deportation goals.

Newark officials have since argued in federal court that GEO Group, one of the country’s largest private prison companies, is operating without a valid certificate of occupancy. After Delaney Hall began housing detainees last week, Mr. Baraka, a Democrat who is running for governor, began showing up regularly and requesting that he and fire officials be allowed to enter and inspect the facility.

Each time, the facility’s personnel turned them away and fire officials issued tickets for code violations.

Federal officials and a GEO spokesman said the mayor had ignored established processes for requesting entry. They have also said that the facility had all the required permits, and have described the mayor’s repeated visits as a political stunt.

On Friday, the dispute escalated significantly.

That morning, Mr. Baraka said he stopped by Delaney Hall to request entry, was denied and left to take one of his children to school. He returned hours later for a news conference that the three lawmakers had planned to hold after touring Delaney Hall.

A security guard opened Delaney Hall’s locked front gate and allowed Mr. Baraka to enter, but barred him from joining the congressional representatives inside, Newark officials said.

“If I was on that property, I was invited there,” Mr. Baraka said Saturday in Newark. “Somebody allowed me. I didn’t climb the fence, I didn’t kick the door down.”

He and several aides waited for more than an hour inside the perimeter of the detention center before he was asked to leave, according to Mr. Baraka and two of his aides.

By that point, Mr. Menendez, Ms. Watson Coleman and Ms. McIver had left the building and were standing near the mayor, according to a video taken by Viri Martinez, an immigration activist who witnessed the arrest.

After several requests that he leave, Mr. Baraka complied, according to two members of his group and video recordings.

“Guy told me to leave, I left. I’m gone,” Mr. Baraka said Saturday.

However, more than a dozen federal agents went out through the gate and arrested him anyway, placing him in handcuffs and leading him away.

Alina Habba, the acting U.S. attorney for the District of New Jersey, has said that Mr. Baraka was arrested after he “committed trespass and ignored multiple warnings from Homeland Security Investigations to remove himself.”

Ms. McLaughlin described the chaotic scene as a “mob,” with the lawmakers, their aides and federal law enforcement officers jostling just outside the facility’s gate.

“We weren’t trying to start anything,” Ms. Watson Coleman said on MSNBC. “We weren’t trying to do anything. We were trying to protect the mayor from what we thought was an unlawful arrest.”

Footage from a body-worn camera shared by Fox News shows the legislators and a scrum of officers outside the facility’s fence. At one point, Ms. McIver appears to make contact with a law enforcement officer in fatigues and a face mask.

A second video also shared by Fox News captures a verbal disagreement between Ms. McIver and several law enforcement officers. Ms. McIver, who is standing with her back against a car and is surrounded by officers in tactical gear, can be heard saying, “Ma’am, he just assaulted me.”

In the video, she and Ms. Watson Coleman walk a few paces away before Ms. McIver stops and turns to face the officers.

“You can’t talk to a congresswoman like that,” she says. “You will pay.”

Mr. Baraka has pushed back against the government’s characterization of the moments before and after he was taken into custody.

“This is all fabrication,” Mr. Baraka told reporters on Saturday. “They get on the media and they lie and lie and lie and lie.”

He said the roughly five hours he spent in custody, before a federal magistrate judge ordered him to be released, were “humiliating.”

By Saturday, Mr. Baraka’s arrest had become a local political flashpoint.

Two of Mr. Baraka’s Democratic opponents in New Jersey’s race for governor — Sean Spiller, the president of the New Jersey Education Association, and Representative Josh Gottheimer — showed up early Saturday at Delaney Hall and spoke to reporters. The three other Democrats running for governor — Representative Mikie Sherrill; Steven Fulop, the mayor of Jersey City, N.J.; and Steve Sweeney, a former State Senate president — also condemned Mr. Baraka’s arrest in statements.

“This is not who we are as a country, certainly not who we are as a state,” Mr. Spiller said at the detention center. “Because right now, we know that folks are scared.”

Mr. Gottheimer added that he and Mr. Spiller were not there as competitors in the June 10 primary.

“We’re here as protectors of democracy,” Mr. Gottheimer said. “We all have to stand up and say to Donald Trump, ‘I don’t think so.’”

Mr. Baraka seemed amused by the candidates’ robust expressions of solidarity.

“I’m glad that they are, you know, making the most of this,” he said with a chuckle.

Across the Hudson River, several New York City lawmakers and Democratic mayoral candidates joined more than 100 protesters at a rally in Lower Manhattan. Speakers praised Mr. Baraka and condemned the city’s mayor, Eric Adams, for working with the Trump administration.

“When they come for the mayors, it’s already pretty bad,” said Brad Lander, New York City’s comptroller who is running for mayor.

Another candidate for mayor, Zohran Mamdani, who represents Queens in the State Assembly, also spoke.

“What Mayor Baraka has told us,” he said, “is you cannot fight extremism with moderation.”

Mark Bonamo and Nate Schweber contributed reporting.