The Senate Intelligence Committee stepped up its investigation of alleged Russian meddling in last year's election Wednesday and subpoenaed former national security adviser Michael Flynn. A Senate historian tells NBC News that this is the first time the Intelligence Committee has used its subpoena power since the congressional investigation of the 9/11 attacks. Committee leaders Sen. Richard Burr, a Republican, and Sen. Mark Warner, a Democrat, say the committee asked Flynn for documents they believe are relevant to the investigation of alleged Russian links. A day earlier, Burr described a subpoena as the "most severe" of the options on the table.
The committee issued the legal order after Flynn's attorneys said they wouldn't cooperate with the investigation unless he was granted immunity from prosecution, sources tell Politico. Burr and Warner say Flynn was asked to voluntarily turn over the documents April 28 but declined. Former Trump adviser Carter Page has also been asked to provide documents. The subpoena was issued a day after Trump's firing of FBI Director James Comey, a move that Burr said makes the committee's work "a little bit more difficult," but not impossible, the Washington Post reports. "The timing of this and the reasoning for it doesn’t make any sense to me," Burr said of Comey's firing. (Read more Michael Flynn stories.)