FBI Director Kash Patel confirmed over the weekend that the agency is investigating New York Attorney General Letitia James' real estate transactions.
The probe is reportedly focused on whether James committed fraud on a mortgage application.
James won a civil case last year against the Trump Organization and Trump himself over allegations of faulty business practices.
She is now the first public official who investigated the president to now face potential criminal prosecutions themselves. The Justice Department has said cases into those who investigated the president are a priority.
James' lawyer said this month the probe focuses on what he calls baseless and discredited allegations.