Migrants held in US 'sanctuary city' as Trump moves army to border

US immigration officers swooped on a New Jersey seafood business, detaining undocumented migrants, officials said Friday, as President Donald Trump deployed troops to the Mexican border.

Trump has pledged a crackdown on migrants with the White House reporting that agents arrested 538 undocumented people nationwide Thursday, with hundreds removed from the country on military aircraft.

"The largest massive deportation operation in history is well underway," White House spokeswoman Karoline Leavitt wrote on X.

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Newark Mayor Ras Baraka said that in a night-time operation in his city, a US Army veteran was among those detained at Ocean Seafood Depot, marking a resumption of workplace raids that were suspended under former president Joe Biden.

"Some ICE (Immigration and Customs Enforcement) agents raided a business in our city without a warrant," Baraka told a briefing.

"The problem with this is that none of these people were rapists or murderers or criminals -- the problem is that ICE went in without a warrant."

Newark, New Jersey, like other major cities including New York, is a so-called "sanctuary city" meaning local officials and law enforcement do not typically cooperate with federal immigration agents.

- 'People are scared' -

Trump has threatened to curb federal funding for cities that uphold sanctuary policies.

Immigration enforcement agents used raids on businesses and workplaces during Trump's first term, and he has vowed to resume them, and to conduct operations at schools, churches and hospitals -- also off-limits under Biden.

"They caught three guys... everybody is afraid, I don't know if this is normal. They were from Ecuador I think," a witness to the Newark raid who declined to be named told NBC News.

Baraka said he was "appalled, upset, angry that this would happen here, in this state, in this country -- that this would be allowed."

On his first day in office, Trump signed orders declaring a "national emergency" at the southern border and announced the deployment of more troops to the area, vowing to deport "criminal aliens."

Active service troops began arriving on the US-Mexico border Friday, with soldiers working to build structures and barracks.

There are an estimated 11 million undocumented migrants in the United States, according to the Department of Homeland Security statistics.

Amy Torres, executive director of the New Jersey Alliance for Immigrant Justice, said "people are scared."

"We knew this was going to happen, and what we learned from folks that stayed behind was that ICE walked in like it was their empire's own conquered land," she said.

"They were heavily armed, there was no prior announcement. They were blocking off entrances and exits."