The director of the FBI is at the center of the House Intelligence Committee's latest battle

By Wednesday morning, the House Intelligence Committee's investigation into Russia's interference in the 2016 election had all but stalled, with the committee's chairman blaming Democrats - and vice versa - for the impasse.

"It appears like the Democrats aren't really serious about this investigation," Rep. Devin Nunes, the committee's chairman, told NBC.

Nunes claimed Democrats had not signed a letter inviting FBI Director James Comey to testify before the committee in a closed session and had not provided their witness list to the committee's majority.

'We always want to keep the committee bipartisan," Nunes said. "But at the end of the day, we're going to do an investigation with or without them, and if they want to participate, that's fine, but the facts of the matter are pretty clear."

His comments took Democrats by surprise. Aides and congressmen who spoke to Business Insider said this was the first they had heard of Nunes' complaints, which they argued were unfounded. Democrats had offered to schedule both a closed hearing and an open hearing with Comey next week, and they did provide a tentative list of additional witnesses to Republicans on Tuesday, according to one aide. They had yet to hear back, the aide said.

A spokesman for Nunes, Jack Langer, said Nunes stood by his claims.

"Both of the Chairman's assertions are true, and we still haven't received a witness list," he said.

In any case, Democratic Rep. Eric Swalwell, a member of the intelligence committee, was incredulous, pointing the finger at Nunes for scrapping a committee hearing that had been scheduled for Tuesday with witnesses both Democrats and Republicans had previously agreed upon: former Acting Attorney General Sally Yates, former Director of National Intelligence James Clapper, and former CIA Director John Brennan.

"We've been in continuous talks with the other side about witnesses we want to hear from," Swalwell said in an interview. "I don't understand how Nunes can cancel hearings and then say it was our fault the investigation's been stalled."

Democratic Rep. Mike Quigley, who also sits on the intelligence committee, agreed.

"We didn't cancel the public hearing, we didn't make a late-night excursion to the White House, we didn't accuse Obama of wiretapping Trump Tower," Quigley told Business Insider on Wednesday. "We haven't played a role in any of those distractions."

Swalwell said the latest impasse stemmed from a battle over whether FBI Director James Comey should appear before the committee again, but in a closed session.

"The chairman requested that in lieu of a public hearing we have a closed hearing with James Comey and Mike Rogers," Swalwell said. "I did not support having one substitute for another. We could have heard from Comey and Rogers in a closed setting, and then held the regular open hearing afterward. In the end, we ended up doing neither."

Quigley said Nunes wanted Democrats to sign a letter asking Comey to appear before the committee in private and would not entertain requests to schedule a second public hearing.

"Up until last week, Democrats and Republicans had gone down this investigative road together," Swalwell said. "I liked Devin Nunes. We worked well with him in the past, and our staff like each other. We functioned quite well."

But things started going downhill quickly when Comey made his bombshell announcement last Monday, during an open House Intelligence Committee hearing, that the FBI was investigating Trump associates' ties with Russia's interference in the US election.

"A lot of our concerns were validated by Comey," Swalwell said.

On Tuesday, Nunes traveled to the White House to view classified executive branch documents he said showed that Trump and his associates had been swept up in incidental government surveillance after the election. The rest of the intelligence committee only learned of the documents' alleged existence the next day, when Nunes gave an impromptu press conference to announce he was going to brief Trump on what he'd found.

"The chairman exited our bipartisan investigation and cut out our ranking member to go and work with the White House and receive classified information that he could have received at the Capitol," Swalwell said. (Nunes has insisted that he couldn't bring the documents back to the Capitol because it would jeopardize their "proper chain of command.")

Nunes' unusual decision to bypass his committee and go straight to the president last Wednesday - with documents that Trump later suggested somewhat vindicated his accusation that President Barack Obama had wiretapped Trump Tower - fueled speculation that the White House had orchestrated the stunt to distract the press from Comey's revelation.

Two days later, Nunes canceled a hearing that would have featured Yates, the former deputy attorney general, who warned the administration in January that former national security adviser Michael Flynn could be subject to Russian blackmail.

Democratic Rep. Jim Himes told CNN Wednesday morning that while most committee members consider Nunes a friend, his behavior had been "aggressive" and "unusual" recently.

Asked why he thought Nunes scrapped the hearing, Swalwell said he can "only say what it looks like, which is that the White House did not want another public hearing that would further validate concerns" about the extent to which Russia's interference "converged" with the Trump team's "personal, political, and financial ties" to Russia.

Quigley didn't go as far. But "whatever he was doing was stuff the White House liked," he said.

Ultimately, Quigley and Swalwell said they're ready to move forward with the investigation.

"We're still going down this road, with the help of the majority or not," Swalwell said. "We still encourage people to share evidence with us that they've found, and we will share it with the Republican members of the committee. We're not going to do what Nunes is doing, and the best thing he can do now is recuse himself."

"It's been a rough 10 days," Quigley said. "But I'm trying to pivot away from 'these guys screwed up.' We have to start moving forward again. The House was ahead of the Senate in this investigation until eight days ago, and we will remain way ahead if we get back to regular order next week, which I believe we will."

It's unclear if Rep. Adam Schiff, the ranking Democrat on the House Intelligence Committee, feels the same way.

"I'd love to get back on track, but I'm not willing to say something is legitimate if it's not," Schiff told CNN on Wednesday night, referring to the investigation's credibility with Nunes at the helm.

"I don't know how to conduct a credible investigation if you have even one person, let alone the chairman, of a committee saying 'I've seen evidence but I won't share it with anyone else,'" Schiff said. "We can't conduct an investigation this way. That's not sustainable. It's not credible."