Washington (CNN) Trump campaign adviser George Papadopoulos' guilty plea Monday appears to hint toward even more threads of the ongoing Russia collusion investigation than what the court revealed.

Lawyers from the Justice Department's special counsel office have repeatedly hinted at how Papadopoulos would contribute to a larger, sensitive investigation.

"The criminal justice interest being vindicated here is there's a large-scale ongoing investigation of which this case is a small part," Aaron Zelinsky of the special counsel's office said during Papadopoulos' October 5 plea agreement hearing , records of which were unsealed Monday.

The special counsel's office sought to keep Papadopoulos' plea agreement confidential because it didn't want to dissuade witnesses and persons of interest from sharing information with investigators.

"Although the government is moving expeditiously to interview individuals of immediate interest to the investigation, news that the defendant has been charged with and pleaded guilty to lying to federal agents may make those individuals reluctant to speak with investigators," the special counsel's office wrote on October 3.

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