[What happens after an ICE raid? Here’s an explaination of the deportation process.]

A backlog of nearly one million immigration cases means that it can take years for a case to wind its way through the courts. Those who were targeted in last week’s raids had been placed on an accelerated docket, with a goal of resolving their cases within a year. The majority had been ordered removed from the country by an immigration judge.

“What we found is that the vast majority did not even show up for their first hearing,” Mr. Albence said. “Above and beyond, we sent them letters giving them the opportunity to turn themselves in and arrange for an orderly removal process,” including time to organize their affairs and schedule flights on commercial carriers.

As part of a multipronged approach to rein in illegal immigration, Mr. Albence said that the government had also been cracking down on companies suspected of hiring undocumented immigrants. He said 3,282 businesses across the country were told last week to submit payroll documents for review.

“Part of our goal is to reduce economic opportunities,” Mr. Albence said. “We cannot have individuals who come into the country illegally and then go find work illegally.”

The audits of companies and payroll forms, often called “silent raids,” hit restaurants, food processing, high-tech manufacturing, agriculture and other industries that employ thousands of workers, according to lawyers representing some of the companies. Employers typically lose a substantial number of workers as a result of the audits, which can also lead to fines and criminal charges against the businesses.

The Trump administration has significantly increased company inspections, often called I-9 audits for the form that workers are required to fill out affirming that they are authorized to work in the United States. There were 5,981 such audits in fiscal 2018 compared to 1,360 the previous year.

“The Trump administration has been more aggressive than any administration with I-9 investigations,” said Kimberley Robidoux, a business immigration lawyer in San Diego who specializes in compliance and who has several clients who are affected.