Senate Foreign Relations Chairman Bob Corker and other prominent Senate Republicans say it’s time for Congress to take on a more exhaustive probe into Russia’s alleged interference in U.S. politics and its contacts with top allies of President Donald Trump.

An ongoing Senate Intelligence Committee investigation of Russia’s actions is no longer sufficient following the ouster of White House National Security Adviser Michael Flynn, Corker told reporters Tuesday. Flynn, who Trump asked to resign after allegations the retired general lied about his contacts with a Russian official, should testify as part of that broader examination, said Corker. of Tennessee.

“I think there needs to be fulsome investigation on all angles relative to nefarious activities that were taking place with Russia, beginning in March but even going back before that time,” Corker said. He said Flynn’s resignation “heightens” the need for GOP leaders to conduct an expanded probe, although he stopped short of endorsing an independent commission as Democrats have demanded.

A number of other Republicans, including the chairman of the House Intelligence Committee, are still downplaying the need to investigate Flynn and said any probe should instead be focused on news leaks about Flynn’s phone call.

Devin Nunes, R-California, said the leaks are “absolutely” the most troubling part of the episode. “We don’t even know this is true,” he said. “We’re going off press reports. So we want to get to the bottom of it.”

Even so, Corker’s comments mark a potentially significant shift for a lawmaker who Trump at one point weighed as a possible secretary of state. Other key Republicans, including Senate Armed Services Chairman John McCain of Arizona and Lindsey Graham of South Carolina, also said Tuesday that Flynn’s resignation is a critical turning point.

Flynn’s White House exit “raises further questions about the Trump administration’s intentions toward Vladimir Putin’s Russia, including statements by the president suggesting moral equivalence between the United States and Russia despite its invasion of Ukraine, annexation of Crimea, threats to our NATO allies, and attempted interference in American elections,” McCain said in a statement.

Graham told CNN Tuesday that tough questions remain about whether anyone else in the White House knew about Flynn’s conversation with Russia’s ambassador shortly after President Barack Obama announced a series of sanctions against Russia ahead of Trump’s inauguration. Flynn in his resignation letter said he had “inadvertently” misinformed Vice President Mike Pence and Trump about discussing sanctions during his talk with the official.

“I think most Americans have a right to know whether or not this was a General Flynn rogue maneuver or was he basically speaking for somebody else in the White House,” Graham said. He also said lawmakers should have access to transcripts of Flynn’s conversations.

House Speaker Paul Ryan, R-Wisconsin, urged all sides to give the administration time to explain more about what transpired.

“I think it’s really important that as soon as they realized that they were being misled by the national security adviser, they asked for his resignation,” he told reporters Tuesday. “I can’t speak to the rest of the circumstances. I think we need to get all of that information before we prejudge anything.”

House Oversight Chairman Jason Chaffetz of Utah rejected the idea of an independent investigation or a probe by his panel. “That situation is taking care of itself,” he told reporters.

Some members of the conservative House Freedom Caucus said intelligence agencies should provide the facts to the relevant committees to decide whether there should be an investigation of Flynn’s conversations with Russian officials. They stopped short of criticizing Flynn’s actions, and said there needs to be a better understanding of the extent to which sanctions were actually discussed.

“It’s incumbent upon the intelligence community and the intelligence committee to work together so we know whether an investigation is warranted,” Rep. Justin Amash, R-Michigan, told reporters.

“If it is impactful, if it goes beyond the scope of what I imagine the intel chairman thinks that it should, I suspect there’s going to be a look-see,” Scott Perry of Pennsylvania said. “But I also get the impression that it was the Russian ambassador that brought up sanctions and that Flynn just acknowledged it and moved on.”

Democrats in both chambers said the matter underscores the need for a broader investigation of Russia’s activities that would be akin to the outside bipartisan commission that examined the Sept. 11 attacks on New York and Washington.

“If the speaker is unwilling to support a full congressional investigation, then he should get out of the way and allow an independent commission to look into the matter,” Rep. Adam Schiff of California, the top Democrat on the House Intelligence Committee, said in a statement. “Russia is a large and growing threat to the United States and liberal democracy around the world.”

So far, GOP leaders have said that the Senate Intelligence Committee will continue to lead the main probe into any contacts between presidential campaigns and Russian officials. The panel announced its probe weeks ago, backed up by subpoena power. Panel Chairman Richard Burr, a North Carolina Republican, said Tuesday that the panel will conduct “active oversight” on the Flynn issue and that he’s inquiring about any transcripts of Flynn’s conversations.

“I can’t verify the facts in the stories but I’ll go where intelligence and the agencies lead us,” Burr said.

The panel’s top Democrat, Mark Warner of Virginia, said he and Burr will meet later Tuesday to discuss the parameters of their investigation. Warner said he views the Flynn resignation as “part of what’s going to be a much larger investigation,” and that Flynn should testify “the sooner the better” as part of it.

But Democrat Chris Murphy of Connecticut dismissed the Senate Intelligence probe as “just an effort to bury this” and that he would prefer a joint committee with the Intelligence, Armed Services and Foreign Relations panels.

He said the situation is getting more serious “by the hour.”

“The White House knew that Flynn had lied and they didn’t do anything about it until they got caught,” Murphy said.

Eliot Engel, the top Democrat on the House Foreign Affairs Committee, was even blunter.

“I cannot remember in my lifetime another crisis, and that includes Watergate, that’s more serious than this one is right now,” he said at a news conference.

House Minority Leader Nancy Pelosi, D-California, asked by a reporter during a news conference about the prospect of Democrats seeking impeachment, snapped: “We’re not here to talk about that. We’re here to talk about accountability to the American people. “

–With assistance from Billy House Anna Edgerton Sahil Kapur and Laura Curtis