To be sure, the number of such prosecutions has always been small.

Both the Obama and Bush administrations unveiled efforts to target employers as they goaded Congress to fix the broken immigration system. Yet prosecutions have rarely exceeded 15 in a single year, according to TRAC. They reached their highest point, 25, in the first year of the Obama administration; they reached 20 in 2005 when President George W. Bush was in the White House.

President Trump has made quashing illegal immigration central to his agenda, and on Friday he is expected to unveil new measures designed to lower the number of Central Americans heading to the United States, most of them seeking work. On Thursday evening, Mr. Trump said the United States would impose a 5 percent tariff on goods from Mexico until the country slowed the flow of migrants.

In the interior of the country, his administration has ramped up payroll audits of companies and workplace raids, leading to the termination of large numbers of undocumented workers. Critics say such enforcement strategies tear families apart rather than address the economic incentives of illegal immigration.

In April, agents rounded up about 280 people at a Dallas-area technology company, in one of the biggest such enforcement actions in a decade. CVE Technology Group was employing people in the United States illegally, according to immigration authorities, who transported the workers to an ICE facility. Most of them were then released but are now in deportation proceedings.

Last June, dozens of workers were arrested at a gardening center in Ohio. Immigration raids have also occurred in Minnesota, Nebraska and Tennessee.