The Senate Select Committee on Intelligence issued a subpoena Wednesday to Michael Flynn, requesting that the beleaguered former national security adviser hand over documents related to the committee's ongoing investigation into Russia's interference in the 2016 election.

The Trump administration asked for Flynn's resignation back in February, after it emerged that he had misled Vice President Mike Pence about whether he'd spoken to a Russian ambassador about lifting Obama-era sanctions on the country. (He had.) Flynn has been at the center of multiple probes into Russian interference ever since, as both the FBI and Congress have sought to understand the links between Russia and the Trump administration and campaign.

The Senate committee already asked Flynn for these documents in April, according to a joint statement by committee chairman Republican Sen. Richard Burr of North Carolina and vice chairman Democrat Sen. Mark Warner of Virginia, but he refused to turn him over. Now Flynn has a choice — submit the documents or stand in contempt.

This news of the subpoena also follows reports that the U.S. Attorney's Office in Alexandria, Virginia, had also sent subpoenas to Flynn's business associates, and that former acting Attorney General Sally Yates had told the White House Flynn had lied to Pence 18 days before the White House actually asked for his resignation.