But some Republicans hailed HSI last spring, as they sought to end a shutdown of its parent agency, U.S. Immigration and Customs Enforcement, following the fatal shootings of two U.S. citizens by federal immigration agents in Minnesota.

When Democrats held up funding for ICE in a push for new guardrails on immigration raids, Senate Appropriations Chair Susan Collins, R-Maine, pointed to the work of HSI as a key reason for ending the shutdown.

“More than a quarter of ICE’s annual appropriated budget is for Homeland Security Investigations, referred to as HSI,” Collins said in a March 12 floor speech.

“HSI’s agents are tasked with combating cartels, human smuggling, child exploitation, forced labor and investigating international financial crimes,” she said. “Do we really want to defund those vital investigations, Mr. President? I think not.”

But Democrats held firm, as some noted that HSI, along with Customs and Border Protection, plays a role in immigration enforcement.

“It’s happening at HSI and CBP,” Sen. Christopher S. Murphy of Connecticut, the ranking Democrat on the Homeland Security Appropriations Subcommittee, told reporters in March, referring to the immigration crackdown. “So, you can’t pretend that you’re not funding immigration enforcement if you’re funding CBP and HSI with no strings attached.”

It remains unclear whether the investigation of Omar, a Minnesota Democrat, falls within the spectrum of work typically conducted by HSI.

Since the probe burst into public view with Monday’s raid, just weeks before the midterm elections, officials have offered no details on the investigation.

“Homeland Security Investigations executed a judicially authorized search warrant secured by the Department of Justice,” the Justice Department said in a statement.  “This enforcement action is part of an ongoing federal criminal investigation.”

According to published reports, the probe centers on immigration paperwork that Omar used to secure legal status and ultimately U.S. citizenship. Omar has said she fled Somalia as a child with her family as the country was gripped by civil war. She secured U.S. citizenship as a minor through the naturalization of her father in 2000.

The Washington Post reported this week that officials are examining whether Omar or her father intentionally misstated her birth date on immigration paperwork so she could be eligible to derive citizenship through him as a minor when he was naturalized.

Collins declined to comment on HSI’s investigation of Omar. The Maine Republican weathered a storm of protests over immigration enforcement in July after a fatal shooting by an ICE agent in her home state. She is now locked in a tight reelection contest that is rated a Toss-up by Inside Elections with Nathan L. Gonzales.

Democratic appropriators also did not respond, although House Democratic leaders issued a statement Monday saying the probe “raises serious questions about the continued corrupt weaponization of the federal government against Donald Trump’s adversaries.”

Omar dismissed the probe as politically motivated. “For ten years, Trump has targeted me with baseless lies and smear campaigns,” she wrote on X. “This is just the latest escalation in his campaign of political intimidation.”

Wide-ranging mission

As the investigative arm of the Department of Homeland Security, HSI has a wide portfolio ranging from probing violations of customs and immigration law to transnational crime, national security threats, terrorism, drug smuggling, child exploitation, human trafficking, illegal arms dealing and financial crimes.

HSI’s workforce of over 10,400 employees includes more than 7,100 special agents assigned across the United States and in 53 countries, according to its website.

The last time that appropriators from both parties outlined specific priorities for the agency was in 2024, under the Biden administration.

They stressed the importance of combating transnational crime overseas, countering fentanyl, fighting child exploitation, and investigating forced labor, including of children, in a joint explanatory statement that accompanied a fiscal 2024 Homeland Security appropriations law. That law provided $2.46 billion for the investigations agency.

A partisan impasse over immigration enforcement techniques triggered a 76-day shutdown of the Homeland Security Department in mid-February,  when the House and Senate couldn’t agree on a fiscal 2026 Homeland Security appropriations bill.

Most of the department finally reopened at the end of April, when Congress agreed to pass funding for everything except immigration enforcement agencies, which included ICE and its HSI division.

To fund those agencies, along with Customs and Border Protection, without any new curbs on immigration agents, Republicans drafted a partisan reconciliation bill that could be passed without the risk of a Democratic filibuster.

That bill included $7.45 billion for HSI, a sum designed to fully fund the investigative agency for the next three years.

President Donald Trump signed that bill into law on June 10.

When lawmakers return to Washington for a lame-duck session next month, the fight over immigration enforcement is sure to resume — particularly if Democrats gain clout in the midterm elections.

“The American people deserve transparency, and we will deliver full accountability for the rogue abuse of power from the Department of Homeland Security and Department of Justice,” House Democratic leaders said in a joint statement.