Senate Minority Leader Chuck Schumer called Tuesday for an "independent investigation," possibly led by career DOJ employees with prosecutorial powers, while Oregon Sen. Jeff Merkley suggested to CNN's Erin Burnett a special prosecutor should be appointed.
"(Flynn's) resignation raises more questions than it answers and the American people deserve the truth," Schumer said at a news conference in the Capitol.
"In the days and weeks ahead, the Trump administration has many serious questions to answer. These questions must be asked by independent and unbiased law enforcement officers. They must be answered truthfully by administration officials, and any attempt to lie or mislead must be countered with the full force of the law," Schumer said.
The Department of Justice declined to comment.
Members of Congress have called for investigations into Flynn's contact in December with the Russian ambassador to Washington and what Flynn might have said about the incoming Trump administration easing sanctions on Russia.
Schumer said it would be inappropriate for Sessions to be involved because he is a long-time political supporter of President Donald Trump, even speaking for him at the Republican convention.
Schumer said he also supports congressional investigations into issues related to alleged Russian hacking of the US political system during the presidential election.
Schumer stopped short of calling for an independent counsel or prosecutor to be appointed.
"What I am calling for is an independent investigation. Are there people in the Justice Department, career people, who could do an independent investigation? Yes, there are. Could there be people appointed as an independent counsel to do an independent investigation? Yes, there could. I am not specifying what there should be. I believe that Attorney General Sessions has no choice but to recuse himself, and then he should and must put an independent investigative authority in charge," Schumer said.
Merkley, however, went further than Schumer Tuesday night when he said on "OutFront" the situation called for a special prosecutor. Like Schumer, Merkley said Sessions could not reliably handle the matter because of his closeness to the President.
"This really merits an independent investigation. It's not an investigation that should take place by Jeff Sessions. Jeff Sessions is too tied to the campaign, too tied to the President. It needs to be an independent or a special prosecutor," Merkley said.
Merkley said he believed an investigation needed to target more than Flynn, offering the possibility that Trump himself is hiding something on Russia.
"The President has talked about how much he admires (Russian President Vladimir) Putin, how much of a buddy he is ... It sounds very likely that there were more conversations than just Michael Flynn by himself," Merkley said, adding, "I'm not asserting that we know for sure, because we don't."
Merkley said that uncertainty necessitated an independent investigation.