WASHINGTON – The Senate Intelligence Committee announced late Wednesday that it sent a subpoena to former national security adviser Michael Flynn for documents related to any contacts with Russian officials that might be relevant to the panel’s investigation into Russia’s interference with the 2016 election.

In a joint statement, Chairman Richard Burr, R-N.C., and Vice Chairman Mark Warner, D-Va., said that Flynn had declined an earlier request to provide the materials voluntarily.

"The committee first requested these documents in an April 28, 2017 letter to... Flynn, but he declined, through counsel, to cooperate with the committee’s request,'' the panel leaders said.

Flynn was fired by President Donald Trump in February, after news reports revealed that the former Army Lieutenant general lied to administration officials about his conversations with Russian ambassador Sergey Kislyak before the inauguration.

Flynn's attorney did not immediately respond to a request for comment about the subpoena.

The committee's request comes as the panel prepares for a Thursday hearing that will feature the testimony of FBI Deputy Director Andrew McCabe and other national security officials.

U.S. Senator Richard Burr

Earlier this week, President Trump fired FBI director James Comey, calling into question the future of the agency's own investigation into possible collusion between Russia and Trump campaign associates.