Federal agents searched Rep. Ilhan Omar’s Washington, D.C., home Monday morning. The Justice Department said it had approved a judicial warrant for the search, which it described as part of an ongoing federal investigation.

The department said Homeland Security Investigations agents carried out the search but did not explain what prompted the investigation. A current federal official described it as a multiyear probe involving whistleblower complaints. A former official said it concerns allegations of immigration fraud; those allegations have not been established.

Omar, a Minnesota Democrat seeking reelection in next month’s midterm elections, condemned the search as an attempt to use federal law enforcement against political opponents. Vice President Vance has previously accused her of immigration fraud, an allegation she denies.