Special Counsel Robert Mueller is investigating the business dealings of President Trump's son-in-law and senior adviser Jared Kushner, according to a new report.
However, the Post's newest dispatch is the first time that it has been specifically reported that the FBI is investigating Kushner's business practices.
The report is based on "officials familiar with the matter".
Mueller's investigation is still in a relatively early phase, and it is unclear if any criminal charges will be brought when it is complete. "It would be standard practice for the Special Counsel to examine financial records to look for anything related to Russian Federation. He will do the same if he is contacted in connection with any other inquiry".
Peter Carr, a Mueller spokesman, declined to comment directly, saying only that "the Special Counsel's Office has undertaken stringent controls to prohibit unauthorized disclosures and will deal severely with any member who engages in this conduct". The Post said the finances of other Trump associates are also being looked into, including former National Security Adviser Mike Flynn, former campaign chairman Paul Manafort and former foreign policy adviser Carter Page.
Last month, the Post disclosed two meetings Kushner had with Russians in December were under scrutiny by investigators.
It was previously reported that investigators were looking into Kushner's December meetings - which were not originally disclosed on his security clearance application - with Sergey Kislyak, the Russian ambassador to the US, and Sergey Gorkov, a graduate of the academy of the KGB's successor organization and the head of a state-owned Russian bank that is subject to American sanctions.
The White House has said the subsequent meeting with the banker was a pre-inauguration diplomatic encounter, unrelated to business matters.
It was a business meeting, occurring because of Kushner's role as head of his family's real estate company, administration officials said.