US federal agents conducted a predawn raid on the home of Democratic US Representative Ilhan Omar on Monday, US media reported.
The search followed a criminal fraud investigation into Ms Omar's immigration paperwork, which was filled out by the Somali-born politician's late father when she was a child, Fox News reported, quoting unidentified sources.
She has repeatedly denied allegations of wrongdoing, calling them false and politically motivated.
“Today in the Washington, DC area, Homeland Security Investigations executed a judicially authorised search warrant secured by the Department of Justice. This enforcement action is part of a continuing federal investigation,” a department representative told AP.
Neither the Justice Department nor a representative for Ms Omar immediately returned The National's request for comment.
Ms Omar was taken to the US as a child, fleeing the civil war in Somalia. She became a US citizen at the age of 17 in 2000 and, in 2018, was elected to Congress to represent Minnesota's 5th District, which includes all of Minneapolis. Ms Omar is seeking another term for the seat on November 3.
An outspoken critic of President Donald Trump, Ms Omar has been a frequent target of his attacks. He has previously suggested she should leave the country.
In February, he said Ms Omar and fellow Democrat Rashida Tlaib of Michigan, who is also Muslim, should be “institutionalised” after they criticised his remarks during the State of Union address.
Mr Trump has also recently attacked Abdul El Sayed, who is aiming to win a US Senate seat in Michigan. Should he win, Mr El Sayed would be the first Muslim elected to the upper chamber of Congress.
Mr Trump has used anti-Muslim language in online attacks against the Democrat, calling him a “jihadist lunatic”.