The bipartisan inquiry, announced jointly by the panel’s Chairman Charles Grassley and ranking Democrat Ron Wyden, was sparked by an exclusive Reuters article from July.
That report revealed details about previously unreported meetings in 2015 set up by the Center for the National Interest, a Washington foreign policy think tank that is supportive of efforts to improve U.S.-Russia relations.
In two separate meetings, Butina, a former graduate student who advocated for gun rights, and Russian Central Bank deputy governor Alexander Torshin together met Stanley Fischer, then Federal Reserve vice chairman, and Nathan Sheets, then Treasury undersecretary for international affairs.
The meetings were documented in a Center for the National Interest report seen by Reuters which discussed arranging the meetings to bring together “leading figures from the financial institutions of the United States and Russia.”
Torshin was sanctioned last April by the Treasury Department, and he is referenced in court records as an unindicted co-conspirator who worked with Butina to infiltrate the National Rifle Association (NRA) and make inroads in conservative political circles to help benefit Russia.
A spokeswoman for the Russian central bank has previously said that Torshin declines to comment on the subject.
The Senate panel earlier this week sent letters to Treasury Secretary Steve Mnuchin, Federal Reserve Chairman Jerome Powell and the Center for the National Interest’s Russian-born CEO, Dimitri Simes, seeking additional information about meetings with top Russian government officials.
“A critical issue facing the Committee and the country is the extent to which the Russian government engaged in efforts designed to undermine our political system and governmental policy through obfuscation and manipulation,” Grassley and Wyden wrote in their letters.
A Federal Reserve spokesman confirmed receiving the letter and said the Fed intends to respond.
Spokespeople for the Treasury Department and the think tank did not immediately respond to requests for comment. Butina’s attorney could not be immediately reached.
In July, Fischer told Reuters he recalled having one meeting with Torshin and his interpreter about the Russian economy and said Torshin also mentioned plans to attend an NRA convention.
Sheets previously declined to comment and a spokesman for him did not have any immediate comment on Friday.
Paul Saunders, the Center for the National Interest’s executive director, previously told Reuters it was unaware of any inappropriate conduct or connections to Russian intelligence services involving Butina and Torshin.
In their letters, Grassley and Wyden said they are asking the think tank for records related to meetings it organized.
“It is concerning that Ms. Butina and Mr. Torshin were able to gain access to high-level administration officials responsible for U.S. economic and monetary policy to reportedly discuss U.S. Russian economic relations,” the lawmakers wrote.
Butina, who is cooperating with prosecutors, is slated to appear in court later this month for a status conference.
Reporting by Sarah N. Lynch; Editing by Sonya Hepinstall