WASHINGTON—Investigators with U.S. Immigration and Customs Enforcement opened about four times the number of workplace investigations in the year ended Sept. 30 compared with the close of the Obama administration, while starting fewer probes into gangs, weapons and financial crimes, according to new figures the agency provided to The Wall Street Journal.

ICE’s focus on workplace enforcement—targeting both immigrants working illegally and their employers—has intensified in the past two years. Homeland Security Investigations, the ICE arm that carries out criminal investigations, opened 6,812 new workplace cases in the 2019 fiscal year, up from 1,701 during fiscal 2016. The agency made 2,048 administrative arrests, primarily of illegal immigrants, up roughly 500 from the year before.

ICE carried out one of its most-high-profile investigations in August, raiding several food-processing plants in Mississippi and detaining about 680 immigrants working in the country illegally.

President Trump has focused his immigration crackdown on preventing new immigrants from crossing the border illegally and discouraging those who do cross from seeking legal protections such as asylum that allow them to stay and work. The data show that, in the past two years, the administration has also put a greater emphasis on enforcement efforts that make it tougher for illegal immigrants to find jobs.

The emphasis on immigration enforcement is new for Homeland Security Investigations, a law-enforcement agency under ICE with a broad mandate to go after international gangs, weapons, drug smuggling and human trafficking. Agents work on cases from bitcoin seizure to art theft.