President Donald Trump's former national security adviser, retired Gen. Michael Flynn, was subpoenaed by the Senate Intelligence Committee on Wednesday.
The committee, led by Sens. Richard Burr, R-North Carolina, and Mark Warner, D-Virginia, said it requested documents that members believe to be relevant to its investigation into alleged Russian meddling in the 2016 presidential election.
The committee initially requested the documents from Flynn in a letter on April 28, but he declined to comply if he wasn't offered immunity. The Intelligence Committee declined the deal and has now followed up with an official subpoena.
Burr and Warner have said they considered their committee's subpoena power as an available recourse.
"I think all options are on the table, and I think you can envision what those options are," Burr told reporters on Tuesday, a day ahead of the announcement.
"I think the most severe would be a subpoena," he said. "I think that the vice chairman and I have, from the beginning, believed that we would make more progress faster with voluntary participation by witnesses, so we have gone to all lengths to exhaust their willingness to do that."
This is the first time the Intelligence Committee has used its subpoena power since the joint inquiry into the terrorist attacks of Sept. 11, 2001, and it's the first time it has subpoenaed documents since the 1970s, a Senate historian told NBC News.
Former President Barack Obama cautioned Trump against hiring Flynn as his national security adviser, but Trump ignored the warning. Obama fired Flynn in 2014 as head of the Defense Intelligence Agency.
Trump still hired Flynn, but he fired him three weeks after the start of his administration because he misled Vice President Mike Pence about conversations he had with the Russian ambassador to the United States about economic sanctions.
Former Acting Attorney General Sally Yates testified on Monday that she told the Trump administration that Flynn had been compromised and could be potentially "blackmailed by the Russians."