DAVOS, Switzerland:  US Robert Mueller, Director of the Federal Bureau of Investigation (FBI) attends the session "Security is an Always-on World" at the World Economic Forum in Davos 26 January 2006.Tthe World Economic Forum this year is gathering more than 2,300 leaders, officials and executives for five days of high-powered networking.  AFP PHOTO PIERRE VERDY  (Photo credit should read PIERRE VERDY/AFP/Getty Images)

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DAVOS, Switzerland: US Robert Mueller, Director of the Federal Bureau of Investigation (FBI) attends the session "Security is an Always-on World" at the World Economic Forum in Davos 26 January 2006.Tthe World Economic Forum this year is gathering more than 2,300 leaders, officials and executives for five days of high-powered networking. AFP PHOTO PIERRE VERDY (Photo credit should read PIERRE VERDY/AFP/Getty Images) NEW YORK, NY - NOVEMBER 03: Donald Trump attends a press conference for the release of his new book "Crippled America" at Trump Tower on November 3, 2015 in New York City. (Photo by Noam Galai/WireImage)
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(CNN) —  

Special counsel Robert Mueller’s confidential report on the Russia investigation is more than 300 pages, according to a Justice Department official and a second source with knowledge of the matter.

The Justice Department official described the still-secret report as more than 300 pages, while a second official said it was between 300 and 400 pages, not including exhibits.

The page length had been a mystery in the days following the announcement that Mueller had concluded his work last Friday, as the Justice Department continually declined to comment on the page count but called it “comprehensive.” Attorney General Bill Barr’s four-page summary of Mueller’s report provided only few details of how it is structured, describing it as “divided into two parts.”

Even many members of Congress have been kept in the dark about the breadth of the report until recently.

A Justice official confirmed that Barr discussed the page length on a call with House Judiciary Chairman Rep. Jerry Nadler on Wednesday. Nadler would only say the report was “very substantial” and less than 1,000 pages when asked by reporters.

Barr on Sunday released a four-page memo stating that Mueller’s investigation did not establish that the Trump campaign conspired with the Russian government before the election, but Democrats have demanded to see Mueller’s full report and the underlying evidence.

A small team at the Justice Department is working on determining what portions of the report can be made public, after scrubbing it for grand jury and other material related to ongoing investigations.

The New York Times was first to report the number of pages in Mueller’s report.

This story has been updated.