Bannon was questioned for hours by Robert Mueller's team over the course of two days, CNN said, quoting a person with knowledge of the inquiry.
Bannon responded to all the questions he faced and no areas were off-limits, this person said, according to CNN.
Bannon was a key strategist to President Donald Trump in his "America First" agenda until he left the administration in August.
He also played a key role in the final weeks of the 2016 presidential campaign and took part in transition meetings that are now being examined.
On Thursday, Bannon appeared before the House Intelligence Committee and thwarted lawmakers from both parties by invoking executive privilege as he declined to answer questions about the transition and his time in the White House.
Mueller's team were expected to ask Bannon about the firings of FBI Director James Comey and national security adviser Michael Flynn, CNN said.
Eyewitness? Submit your stories now via social or:
Email: eyewitness@pulse.ng
![The 10 warmest years have occurred since 2007 [Black Doctor]](data:image/svg+xml;charset=utf8,%3Csvg%20xmlns%3D'http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg'%20width%3D'300'%20height%3D'172'%20data-ring-placeholder%3D'1'%3E%3C%2Fsvg%3E "The 10 warmest years have occurred since 2007 [Black Doctor]")
