The subpoenas seek business records from individuals who had worked with General Flynn on contracts after he was let go as Director of the Defense Intelligence Agency in 2014, as reported by CNN on Tuesday.
Comey's firing prompted a storm of criticism from Democrats, who accused the president of seeking to stall the probe.
The Federal Bureau of Investigation is looking into allegations Russian Federation meddled in the 2016 presidential election to benefit Trump, as well as possible links to the Trump campaign.
The Senate Intelligence Committee has subpoenaed documents from Michael Flynn, President Donald Trump's fired national security adviser, in a sign the bipartisan probe will continue full speed ahead one day after Trump terminated Federal Bureau of Investigation (FBI) director James Comey.
It was the committee's first subpoena in the Russian investigation.
Flynn resigned from his position as National Security Advisor on February 13, after holding his role for only 23 days.
Flynn was paid $45,000 for an appearance in Moscow celebrating Russia Today, which is a Russian-funded news outlet that USA intelligence agencies have said helped publish and promote stolen emails that were meant to harm Hillary Clinton's president campaign.
WHO Confirms New Ebola Case in Democratic Republic of Congo
World Health Organization made the announcement on Friday, May 12 following the deaths of three people from the dreaded disease since April 22.
As for why, exactly, the president is so inclined to praise the former NSA he fired, Rachel noted an interesting article in The Atlantic, published yesterday. He was also paid $530,000 past year by a businessman linked to the Turkish government, all while serving as an adviser to the Trump campaign.
Mr Stone, Mr Page, Mr Flynn and former Trump campaign chairman Paul Manafort all received similar requests for information, a source familiar with the Senate investigation said.
Obama aides also described Flynn as notably dismissive of the threat Russian Federation posed to the United States when discussing policy in transition meetings with outgoing national security adviser Susan Rice and other top officials.
US Attorney Dana Boente, whose office issued the subpoenas, is also leading the investigation into WikiLeaks and the effort to bring possible charges against the group's founder, Julian Assange.
An Obama administration official who warned the Trump White House about contacts between one of its key advisers and Russian Federation is set to speak publicly for the first time about the concerns she raised.
The FBI began an investigation in July into possible ties between Trump campaign associates and Russian Federation during the 2016 presidential campaign. She had been scheduled to appear in March before the House intelligence committee, but that hearing was canceled.