Former Trump adviser Peter Navarro has revealed in a court filing that he has been subpoenaed to appear before a grand jury this week as part of the Justice Department's probe into the deadly U.S. Capitol insurrection. Navarro said Tuesday he was served by the FBI at his Washington, D.C., house last week.

The subpoena is the first known instance of prosecutors seeking testimony from someone who worked in President Donald Trump's White House as they investigate the worst attack on the Capitol in two centuries.

The Navarro subpoena could signal the Justice Department is widening its probe to examine the activities and records of people who worked directly for the Republican president.