(CNN) Possible collusion between Trump associates and Russians remains a subject of investigations by the House and Senate intelligence committees, contrary to assertions from President Donald Trump and White House officials that there's no evidence of collusion, multiple sources in both parties tell CNN.

"The committee is drawing no conclusions at this time, and will continue follow the facts where they lead," GOP Sen. Richard Burr, the chairman of the Senate intelligence committee, told CNN.

Such possible collusion is "the whole underlying premise of the investigation," a House Democratic source involved in the investigation said.

Another member of the Senate committee told CNN that possible collusion "is what we are investigating."

Sen. Mark Warner, vice chairman of the Senate Select Committee on Intelligence, said while attempted Russian interference is clear, the question of whether there was collusion is still unknown.

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