"For ten years, Trump has targeted me with baseless lies and smear campaigns," Omar said in a statement. "This is just the latest escalation in his campaign of political intimidation. I will not be silenced."

Her communications director Jacklyn Rogers called the raid "an outrageous abuse of power" by the Trump administration. "The Congresswoman has done nothing wrong."

The nature of the criminal investigation remains unclear.

A BBC crew saw several agents at the home, some carrying boxes to a van. News of the search was first reported by Fox News, which has said the investigation is about immigration paperwork filed by her late father when Omar was a child.

The timing of Monday's raid - 22 days before the November midterm elections which will decide the balance of power in Congress for the next two years - has raised concerns from Democrats who have rallied behind Omar.

The justice department has a longstanding policy of refraining from most enforcement action that is "likely to raise an issue or the perception" it was being brought for the purpose of affecting any election or disadvantage a candidate.

The US House Democratic Party leadership said in a statement that Omar had long been targeted with "vile personal attacks and baseless accusations" by Trump.

"Now, less than 30 days until the midterm election, his violent mass deportation machine has descended upon the home of a duly elected Member of Congress and her family," it said.

Omar's immigration records have been scrutinised in the past by Republicans. Earlier this year, fellow Congresswoman Nancy Mace of South Carolina unsuccessfully filed a subpoena of her records.

Last month, Homeland Security Secretary Markwayne Mullin told a conservative podcaster "something is going to happen", making allegations of marital fraud against Omar.

Separately, the White House border tsar Tom Homan told Fox News that Omar was being investigated for unspecified immigration violations.

Omar denied these allegations last month. "I will say it again so it's as clear as possible: I'm not at all worried about these investigations, because they are complete shams," she said in a campaign fundraising email, an archive of which has been seen by the BBC.