The FBI is investigating whether foreign governments, organizations or individuals provided financial support to extremists who helped plan and execute the January 6 attack on the Capitol, one current and one former FBI official told NBC News, the latter reported.

As part of the investigation, the bureau is examining payments of $500,000 in bitcoin, apparently by a French national, to key figures and groups in the alt-right before the riot, the sources said. Those payments were documented and posted on the web this week by a company that analyzes cryptocurrency transfers. Payments of bitcoin, a cryptocurrency, can be traced because they are documented on a public ledger.

Separately, a joint threat assessment issued this week by the FBI, the Department of Homeland Security and various other federal and D.C.-area police agencies noted that since the Jan. 6 riot, "Russian, Iranian, and Chinese influence actors have seized the opportunity to amplify narratives in furtherance of their policy interest amid the presidential transition."