Washington CNN  — 

Several investigators on Robert Mueller’s team have expressed frustration to people outside the special counsel about the way the investigation findings were summarized by Attorney General Bill Barr in his letter Congress, according to sources familiar with the conversations.

In particular, some investigators felt the letter did not adequately describe how the investigation of obstruction included derogatory information about President Donald Trump’s actions, according to one of the sources. Barr’s letter obliquely referenced evidence on both sides of the issue, but did not explain it further.

In addition, there has been frustration on the team that the Justice Department has helped shape the public perception of the report but the special counsel cannot address discrepancies between the summary and the actual findings, according to another source familiar with the matter.

Concerns were first reported in The New York Times and The Washington Post this week.

Mueller’s team wrote summaries of the findings and expected more of that to be used, one of the sources said.

Another source with knowledge of the summaries described them as part of the confidential report that is being reviewed for release to Congress and the public. But the source strongly disputed that they were written in a way that allowed for immediate release, because of sensitive information that needed to be considered for redactions.

The Department of Justice said Thursday in a statement every page of the report was marked as possibly containing information that should not be publicly released and that Barr released his letter about Mueller’s main findings because of the “extraordinary public interest in the matter.” The statement said the understanding was the report itself would be released after needed redactions and that Barr wrote the letter “without attempting to summarize the report.”

But the reported discrepancies are exacerbating concerns about Barr’s handling of the Mueller report among Democrats on Capitol Hill. On Thursday afternoon, House Judiciary Chairman Jerry Nadler demanded in a letter to Barr that the attorney general publicly release the Mueller summaries “as soon as possible,” and he requested communications between the special counsel and the Justice Department about the report.

“I think that these questions just show again why we need the full Mueller report … with all the underlying documents released,” Nadler told CNN Thursday. “It would also answer the question of why the summaries that were allegedly prepared by Mueller’s team were not released. All these questions would be answered by releasing the report. And yes, I think it’s inevitable that Mueller is going to testify at some point, but the first thing we need is the release of the report and the documents.”

Another source familiar with discussions at the Justice Department ahead of the conclusion of the report suggested that what could be at issue is the description of the evidence for obstruction that Mueller considered but was only referenced briefly in Barr’s letter, rather than there being any single alarming incident about obstruction that has not been disclosed. Barr, in his letter, included that Mueller had found evidence on both sides in the consideration of obstruction, but opted in the end to not make a conclusion. Barr also included that much of the evidence on obstruction is publicly known.

While the investigation was extensive with some 500 interviews, Mueller’s investigators did not get to talk to some key figures, including the President and his son, Donald Trump Jr., who would have had insights into both the June 2016 Trump Tower meeting and also how the misleading statement to the press about the meeting was crafted. Trump Jr. did testify to multiple congressional committees. His attorney has declined to comment.

An administration official expressed some frustration with Democratic demands to see as much of the Mueller report as possible. The official complained that the report should not reveal information that is embarrassing about the President if he’s not being accused by the special counsel of committing any crimes. That official called that possibility “sh***y.”

This story has been updated with additional developments Thursday.

CNN’s Manu Raju, Pamela Brown and Jim Acosta contributed to this report.