WASHINGTON—The Trump administration’s investigation into Rep. Ilhan Omar (D., Minn.) is aimed at building a case to strip her of her U.S. citizenship and ultimately deport her, according to U.S. officials and other people familiar with the probe.

The multipronged effort is focused at least in part on how Omar obtained her citizenship after she arrived in the U.S. from Somalia decades ago. Investigators are focused both on the congresswoman and actions of her deceased father, some of the people familiar with the probe said. Nur Omar Mohamed brought his daughter and other family members to the U.S. from a refugee camp in Kenya in 1995.

Omar’s Washington, D.C., home was searched by federal agents early Monday, three weeks before the midterm election, in which she is seeking-re-election. The Justice Department said Homeland Security agents executed a court-authorized search, but it declined to elaborate.

Items taken from Omar’s home included her cellphone, notebooks, personal computers and her passport, some of the people said. Only the congresswoman and her husband were home at the time of the search.

Authorities have also issued more than a dozen subpoenas, including to some of Omar’s relatives, seeking testimony before a Minnesota grand jury, a person familiar with those proceedings said. Among other things, the investigation is looking at her family’s immigration paperwork, the person said.

In a Wall Street Journal interview earlier this year, Omar said she never committed immigration fraud.

“President Trump would love to eliminate one of the most effective progressive voices in Congress. There is no basis for this,” her office said in a statement Wednesday.

The Trump administration has made an unprecedented effort to denaturalize U.S. citizens by proving they lied in the process of obtaining citizenship, filing dozens of lawsuits. Omar’s case, if it proceeds, could become the highest-profile—and most controversial—part of that effort. The president has long called for Omar’s deportation, using her as a rallying point for the GOP’s anti-immigrant and anti-Muslim wings.

On Monday evening, an Ohio audience Trump was speaking to chanted “deport” after he talked about Omar and other Somalis. “They cheat on everything,” he said. “We’re not going to stand for it.”

Omar, 44 years old, has long been a top target for GOP-led investigations. A welfare-fraud scandal in Minnesota—heavily tied to defendants of Somali descent—has added fuel to the fire.

At the center of the immigration investigation is whether Omar or her father changed her age on her citizenship application to show she was 17 years old rather than 18, according to people familiar with the probe. If Omar was 17 at the time her father applied for citizenship, she would have qualified automatically rather than needing to pursue her own immigration process. She became a citizen in 2000.

Officials at Homeland Security Investigations looked into a similar tip under the Biden administration, according to people familiar with those efforts, but they decided not to move forward because they lacked evidence of fraud.

The government can’t simply strip a person of their U.S. citizenship. The Justice Department must file a lawsuit in federal court and prove that the person lied in a material way to gain their citizenship. Most of the cases the Justice Department has filed this term haven’t yet been decided.

Leon Fresco, a top immigration official in the Justice Department during the Obama administration, said the Trump administration’s case would hinge on finding material evidence that Omar lied about her own age, rather than her father lying on her behalf.

“That would make the case significantly easier to prosecute,” he said. “But either way, they are not traveling a well-paved road here.”

Administration officials have touted what they say is the most wide-ranging effort in Justice Department history to strip people of their citizenship. In all, the administration has filed more than 200 lawsuits against convicted criminals and others it is seeking to denaturalize. Before Trump took office this term, denaturalization cases were rare, with the government filing roughly a dozen or fewer a year, according to the Transactional Records Access Clearinghouse, a nonprofit that tracks federal immigration data.

Jeanine Pirro, the U.S. attorney in Washington, said her office was also investigating Omar’s financial disclosures.

“There are several investigations going on,” Pirro said Tuesday on Fox News. “If there was a crime that was committed it will be prosecuted.”

Pirro said it “doesn’t matter” that a nonpartisan entity charged with reviewing misconduct allegations involving members of Congress earlier this year cleared Omar of wrongdoing in connection with documents she submitted to Congress that dramatically overstated her wealth.

Born in Mogadishu, Somalia, in 1982 into an affluent family, Omar initially settled in the suburbs of Washington, D.C., before her family moved to Minnesota as she entered high school.

She lost her mother when she was in preschool, according to her book, “This Is What America Looks Like: My Journey From Refugee to Congresswoman.” As a self-described spoiled youngest child, she was raised by her father and a collection of family members.

Omar’s father died in June 2020 at age 67 from what she has said were complications from Covid-19. In the U.S., he worked as a cabdriver and postal worker.

Allegations of immigration fraud have surrounded Omar since she first ran for public office in 2016, when she won a seat in the Minnesota House. Those questions have often been tied to her multiple marriages.

Secretary of Homeland Security Markwayne Mullin told a conservative podcaster last month that there was a continuing federal investigation into Omar, who he said “married her brother to try to bring him into the United States.” It is a claim Trump has repeatedly made. She has denied it for more than a decade.