Some Democrats involved in the impeachment inquiry are beginning to suspect that certain witnesses have coordinated with each other ahead of testifying to ensure their stories do not conflict—the very outcome investigators are trying to avoid by conducting hearings behind closed doors.

Two Democratic lawmakers told The Daily Beast that, over the course of the nine witness depositions they have conducted over the last several weeks, there have been suggestions that certain witnesses spoke to each other about what they would say to impeachment investigators.

“We have direct evidence from our investigation that witnesses have talked to each other about their testimony,” said Rep. Eric Swalwell (D-CA), a member of the House Intelligence Committee, adding that the evidence concerns two witnesses in particular, whom he declined to name.

And Rep. David Cicilline (D-RI) said, “There’s some testimony already that has suggested there has been conversation” among witnesses.

“We’re working very hard to protect the integrity of the investigation and prevent witnesses from sharing their testimony with each other,” he said. “You can only do that so much.”

House Democrats have argued that, at this early stage in the impeachment inquiry, proceedings need to happen behind closed doors so that witnesses aren’t aware of exactly what other witnesses are saying and, therefore, aren’t able to adjust their stories so that they’re all on the same page.

That witnesses might coordinate, Swalwell said, is concerning “because they would tailor [testimony] to try and help each other or manufacture alibis.”

Doing so while lying under oath, of course, is a crime—something that several Democrats believe may have been committed by at least one witness, U.S. Ambassador to the European Union Gordon Sondland. Short of that, less-than-candid testimony from witnesses threatens to undermine the investigation that Democrats are attempting to conduct, all while they get attacked relentlessly by Republicans for not holding hearings that are open to the public.

On Wednesday, President Trump’s defenders in the GOP escalated their opposition by storming the secure room in the U.S. Capitol where depositions have been taking place, grinding the impeachment inquiry to a halt—if only for a day—as they demanded Democrats open up the proceedings to the country.

Of the witnesses Democrats have heard from in closed-door sessions so far, most have been career State Department or Pentagon officials, who have raised alarms over how Trump and his allies pressured Ukraine to open up investigations into the president’s political rivals while holding $400 million in security aid over their heads. Two of those witnesses, Sondland and former U.S. special envoy to Ukraine Kurt Volker, are connected to Trump personally and are linked to carrying out the president’s Ukraine plans. If Democrats have their way, they will soon be hearing testimony from other witnesses in that category.

“Anything that’s not patently illegal, they’re going to try to get away with,” said one lawmaker with knowledge of the proceedings of some of the Trumpworld witnesses.

But several lawmakers involved in the impeachment inquiry acknowledged it would be inevitable that at least some of the witnesses—many of whom have personal relationships with each other after working in similar places in government—might speak to each other as the inquiry unfolds.

“Certainly, that’s the thing we want to avoid,” said Rep. Harley Rouda (D-CA), who said he could not “opine” on whether it was clear that certain witnesses had coordinated with each other in the midst of the impeachment inquiry. “But that doesn’t mean that these witnesses haven’t talked to each other over the last few months, because they're all operating in the same theater of Ukraine—many of them, obviously.”

But several other Democrats who are participating in the inquiry are not under the impression there is any widespread effort afoot by certain witnesses to deny candid testimony to the impeachment committees.

Rep. Jim Himes (D-CT), also an Intelligence panel member, said he personally did not believe that witnesses had been coordinating with each other. “I take that very much with a grain of salt,” he said. “Nobody has come in other than Sondland, maybe Volker, that could somehow be regarded as complicit here.”

“I mean, it could be… I don’t think that’s right,” added Himes. “But [Swalwell] could be seeing something I’m not seeing.”