The Senate Intelligence Committee has invited former Trump campaign aide Sam Nunberg to appear before the panel as part of a closed-door testimony and provide them with documents of his correspondence with longtime Trump confidant Roger Stone that concern Russia, WikiLeaks, and hacking.

“The Senate Select Committee on Intelligence is conducting a bipartisan inquiry into Russian interference in the 2016 US election,” the panel’s request says, according to media reports. “As part of that inquiry, the Committee requests that you make yourself available for a closed interview with bipartisan Committee staff at a mutually agreeable time, and also requests that you produce and preserve certain documents.”