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.

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

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