The Senate Judiciary Committee just made public today the existence of two letters written by Chairman Chuck Grassley, one sent to the FBI and the other sent to the Office of the Special Counsel (which is a permanent agency separate from Robert Mueller’s operation.)
The gravamen of the dispute appears to be that Grassley has learned that FBI employees only spoke with the Office of the Special Counsel because Special Counsel Office members agreed to sign nondisclosure agreements. The agreements specify that SCO members must redact "any disclosure to Congress, any senator or member of Congress and/or any congressional committee, subcommittee or other congressional establishment," which led Grassley to comment that "the FBI held key information hostage." Grassley wrote in his two letters that this was the first time the FBI has required members of the special counsel office to sign such agreements as part of an investigation [of the Comey firing and by extension Trump Russia.] Newsweek:
In his letter on Monday, Grassley asked the special counsel office to provide the nondisclosure agreements and also notify the committee in the future "of any attempt by any agency under its jurisdiction, in any matter, to obtain an NDA that purports to limit the rights of the committee to obtain information from the OSC." He also asked that the FBI explain to the committee why it sought the nondisclosure agreements.
Also on Monday, the Senate Judiciary Committee requested information from the CIA related to Russian meddling in the election. The committee is one of three congressional panels looking into the Russia matter.
A spokesperson for the FBI declined to comment, saying it would provide any response to the Senate Judiciary Committee. A spokesperson for the Office of the Special Counsel also declined to comment.
It would appear on its face that Robert Mueller is keeping the flow of information between the FBI and the Office of the Special Counsel tightly under wraps, which considering the fact that our government got hijacked during the 2016 election by an hostile alien power seems quite prudent.