Story highlights FBI Director James Comey briefed senators on Russia Friday in a closed-door meeting

The Senate Intelligence Committee is building its investigation into Russian interference in the US elections

Washington (CNN) FBI Director James Comey discussed Russia with members of the Senate Intelligence Committee Friday afternoon, as questions swirl about how expansive lawmakers will make their investigations into Russia's influence in last year's election.

A parade of top senators, including members of the Democratic and Republican leadership, darted into a Senate meeting room Friday afternoon at the end of a week that began with the resignation of national security adviser Michael Flynn over questions about his calls with the Russian ambassador to the US.

The senators were tight-lipped as they left the meeting to start their week-long recess, but one attendee said the closed-door briefing was about Russia. Florida Republican Sen. Marco Rubio, who was at the meeting, would not comment afterward but later tweeted: "I am now very confident Senate Intel Comm I serve on will conduct thorough bipartisan investigation of #Putin interference and influence."

I am now very confident Senate Intel Comm I serve on will conduct thorough bipartisan investigation of #Putin interference and influence — Marco Rubio (@marcorubio) February 17, 2017

Lawmakers have been working swiftly behind the scenes to set the scope of their investigations -- which now number three -- into Russia's influence in the US elections. Pressure grew on Congress to expand their focus this week following reports that Russian officials were in frequent contact with President Donald Trump's campaign during the election.

Sen. Mark Warner, the top Democrat on the Intelligence committee, did not answer questions about the focus of the Comey briefing Friday. But he did talk about the extent of the investigation he is building with Senate Intelligence Chairman Richard Burr.

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