(CNN) The Special Counsel's Office is hoping to deny an attempt by several media organizations, including CNN, to unseal documents in the Russia probe, by arguing that the documents need to remain private because of the breadth of still-secret parts of the ongoing investigation.

"The Special Counsel's investigation is not a closed matter, but an ongoing criminal investigation with multiple lines of non-public inquiry. No right of public access exists to search warrant materials in an ongoing investigation," Robert Mueller's team wrote in a filing Wednesday night.

The prosecutors wrote in the firmest language yet about how their yearlong investigation into Russian interference in the 2016 US election continues and includes several interconnected parts, some of which may link back to searches of the belongings of former Trump campaign chairman Paul Manafort that were also used to build cases against him unrelated to his work for the campaign.

Manafort faces criminal indictments in Virginia and DC federal courts related to his foreign lobbying business from before the campaign. He's pleaded not guilty in both.

Prosecutors have previously revealed that the Justice Department directed Mueller to look into allegations that Manafort coordinated with Russians during the campaign, yet they have not previously hinted that others besides Manafort could be central to the Russia probe. Wednesday's court filing acknowledges multiple relationships that are part of investigative threads.

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