(CNN) The FBI informed House Republicans late Friday evening that it has "substantially complied" with two committees' document requests related to the Russia investigation, but correspondence obtained by CNN shows several issues remain outstanding, likely prolonging the ongoing battles between Capitol Hill and the nation's top law enforcement agencies.

In letters to House Intel Committee Chairman Devin Nunes, House Judiciary Committee Chairman Bob Goodlatte and House Oversight Committee Chairman Trey Gowdy, the FBI provided a highly detailed update of what records have been provided to date in response to congressional subpoenas related a wide-ranging set of topics, including the Hillary Clinton email investigation, surveillance orders under the Foreign Intelligence Surveillance Act on Trump campaign associates, the infamous dossier compiled by Christopher Steele on Trump and Russia, and questions about how confidential human sources were utilized by the FBI in the Russia investigation. However, the FBI said it needs to "further engage with the Committee to better understand the information sought" on a request related to the Clinton Foundation.

The process has proved to be a death by a thousand cuts for the Justice Department and FBI, as officials continue to turn over documents in the midst of an ongoing criminal investigation into Russian interference in the 2016 election -- often initially scoffing at the breadth of requests to only acquiesce months latter.

Nunes regularly goes on Fox News to threaten Deputy Attorney General Rod Rosenstein with contempt of Congress, but no real movement has ever progressed in the House on that front. Democrats have raised concerns that the effort is an attempt to give the President a reason to fire Rosenstein, who is in charge of Special Counsel Robert Mueller's investigation into potential collusion between Trump associates and Russia.

On Friday, CNN reported that GOP sources briefed on the dispute between the Justice Department and House Republicans were well aware not all of the requests had been satisfied yet, but it was unclear what steps will be taken at this point.

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