Federal authorities raided the Washington, D.C., home of Rep. Ilhan Omar on Monday morning as part of a criminal investigation of the Minnesota Democrat.

Omar, who has not been charged with a crime, said she was being targeted for political purposes because of her opposition to President Donald Trump.

A person familiar with the situation, who spoke on condition of anonymity to discuss the nonpublic investigation, told CNBC that the probe of the 44-year-old congresswoman is complex and has been going on for years.

MS NOW reported that a law enforcement source with direct knowledge of the raid — which comes weeks before November’s midterm election — said the investigation into Omar is based on allegations of fraud.

Fox News, which first reported the raid, cited a source familiar with the probe as saying it is focused on her immigration paperwork, which was filled out by her father when she emigrated to the U.S. with him from Somalia as a child.