It was a typical summer morning at a Mexican supermarket in New Jersey. Hispanic workers stocked shelves at El Oaxaqueño with chiles and condiments from Latin America. Regulars ate steak-stuffed tacos on freshly made tortillas in the adjacent cantina.

Day laborers idled in the drab parking lot, hoping to score informal work in landscaping or construction. Suddenly, more than half a dozen S. U.

V.s swarmed the lot and federal immigration officers leaped out, according to accounts from people at the scene. Laborers scrambled, and officers chased at least one man into the supermarket, past the colorful piñatas hanging by the entrance, workers in the market said. Customers and workers tried to hide — upstairs, in the bathroom, behind crates of produce in the walk-in refrigerator.

But immigration agents found them and, one by one, zip-tied their hands and whisked them out the back door. The raid, on June 24, which has not previously been reported by the news media, appears to be among the largest sweeps in the region since the Immigration and Customs Enforcement agency quietly revamped its operations this summer. They opened the door and pulled us out, Bernarda Hernandez, 32, a Mexican worker, said in Spanish.

She had locked herself in the bathroom with another female worker and said she pleaded in vain, telling the officers that she had a 2-year-old daughter. I was traumatized. In just about an hour, ICE arrested Ms. Hernandez and 17 other people without legal status after descending on the parking lot because of a reliable tip that a criminal illegal alien, with charges for theft and forgery, was at that location, the Department of Homeland Security said in a statement.

The agency said that some people fled into the supermarket, forcing officers to initiate a pursuit. The agency did not specify how many people it arrested inside, but most of those detained appeared to be collateral arrests — bystanders without legal status who were not the original targets of ICE. Witnesses said in interviews that the officers detained 10 people inside El Oaxaqueño, including six workers, from shelf stockers to the butcher.

A handful of day laborers were detained outside. The new ICE activity, more discreet and dexterous than the highly visible raids in large cities last year, has surprised towns, suburbs and cities across the United States. Agents have fanned out under orders to make 2,000 immigration arrests a day — roughly double the pace from this spring.

The Trump administration launched the surge with little showmanship after shaking up the leadership at the Homeland Security Department, promising to avoid the large raids that led to political blowback after agents killed two U.S. citizens in Minneapolis in January. The crackdown has gained steam with less than three months before the midterm elections, as Republicans seek to retain control of Congress. The more nimble approach appears to come in response to polling that has shown that the hard-line aspects of President Trump’s immigration agenda are a vulnerability for the party.

In New Jersey, ICE arrested more 2,100 people in July, the most in one month since Mr. Trump returned to power and more than double the roughly 850 to 950 people that the agency was arresting on a monthly basis from February to May, according to ICE data released on Monday by Deportation Data Project, an academic group. That’s more people than ICE arrested in nearby New York, a larger state with a bigger immigrant population where arrests also spiked to more than 1,500 in July, according to the data. ICE operations in our communities do not make New Jersey any safer, said Stephen Sigmund, a spokesman for Gov.

Mikie Sherrill, a Democrat who has opposed new ICE detention centers in New Jersey and sought to ban agents from wearing masks. The spike in arrests has come into focus in New Jersey through bursts of early morning arrests largely out of the limelight. Plainclothes agents in masks have resurfaced in tow...