Bannon spent a total of about 20 hours in conversations with Mueller and his team, NBC News said, citing two unnamed sources.
Earlier on in the day, House Intelligence Committee Ranking Member Adam Schiff said the committee will likely initiate contempt proceedings against Bannon after he refused to answer questions during testimony on Thursday.
"He [Bannon] refused to answer almost all of the questions," Schiff said on Thursday. "In terms of next steps, I think the next step for the Congress to take — initiate contempt proceedings."
The congressman explained that Bannon refused to answer questions about conversations he had after the 2016 presidential campaign and after he left the Trump administration.
Schiff said Bannon has done the impossible by bringing together Democrats and Republicans on the Intelligence Committee. There is a broad bipartisan agreement that Bannon’s testimony and use of executive privilege is insupportable, Schiff added.
The United States has repeatedly accused Russia of interfering in the 2016 presidential election and is investigating allegations of collusion between Russia and the Trump campaign. Trump and top Russian officials have repeatedly refuted the allegations.