(CNN) - Some Democratic lawmakers believe that former national security adviser Michael Flynn is cooperating with lawmakers looking to find out if he misled officials on his security clearance form.
"Clearly he's been looking for immunity for some time. He said he would come in and talk to us at the intel committee, but only with immunity," Sen. Mark Warner told CNN's Chris Cuomo Tuesday on "New Day." "I would have a lot of questions for General Flynn, not only his unreported trips and unreported finances he received from Turkey, from Russia. I'd like to know what kind of conversations he had with Russian officials while he was directly involved in the campaign."
A pair of top House Democrats are digging into whether Flynn may have misled officials on his security clearance form about two Middle East trips -- including one reportedly about building $100 billion worth of nuclear energy plants with help from Russia's nuclear power agency.
Flynn was forced to step down as national security adviser just weeks after President Donald Trump took office after reports surfaced that Flynn misled the administration about his conversations with the Russian ambassador.
House Democrats have demanded documents from Flynn about the information and Sen. Sheldon Whitehouse told CNN's Wolf Blitzer Monday that Flynn appears to have been responsive.
"All of the signals are suggesting that he's already cooperating with the FBI and may have been for some time," the Rhode Island lawmaker said on "The Situation Room." "One of the more talkative people in 'Trumpland' has gone absolutely dead silent and that's what prosecutors strongly encourage cooperating witnesses to do."
During the 2016 presidential campaign, Flynn was one of Trump's more vocal surrogates -- especially when it came to criticizing Democratic nominee Hillary Clinton.
"It could be a huge deal, because who knows what Trump has said to him, both during the campaign and during the early days of the presidency," Whitehouse added. "Apparently Trump has been in touch with him after his firing from the White House to tell him to stay strong, which, in some circumstances, could be looked at as manipulation of a witness or obstruction of justice."
House investigators note that they do not know precisely when Flynn traveled to the Middle East for the nuclear deal, but they cite a discrepancy between the June 10, 2015, testimony he gave to the House foreign affairs committee and the official August 2015 start date he lists with a consulting company.