President Trump's son-in-law Jared Kushner, a senior White House advisor, is under scrutiny by the FBI as part of their Russia probe, according to US reports.
Investigators believe Mr Kushner has significant information relevant to their inquiry, officials told NBC News.
However unlike President Trump's former aides Paul Manafort and Michael Flynn - who are formally considered subjects of the FBI investigation - they say Mr Kushner might not be suspected of any crime.
Mr Kushner had meetings with Moscow's ambassador to the US, Sergey Kislyak, and Russian banker Sergey Gorkov in December last year.
His lawyer Jamie Gorelick told NBC News: "Mr. Kushner previously volunteered to share with Congress what he knows about these meetings. He will do the same if he is contacted in connection with any other inquiry."
The FBI and the oversight committee - as well as several other congressional panels - are looking into Russian meddling in the 2016 presidential election as well as possible connections between Russia and the Trump campaign.