Washington (CNN) Prosecutors have confirmed that there's an "ongoing criminal investigation" that relates to Julian Assange's case, according to an assertion they made in court on Wednesday.

The Justice Department wrote to a judge in the Eastern District of Virginia that it needed to keep a document in the case from more than a year ago still secret because of the ongoing activity.

The extent of the continuing investigative work around WikiLeaks and Assange is still unknown -- though it confirms CNN and other news outlets' reporting in recent days that WikiLeaks is connected to at least one probe that could result in more criminal charges.

This admission by prosecutors of the ongoing investigation bolsters CNN's reporting Tuesday that several tentacles related to WikiLeaks -- including the pursuit of testimony from a former Roger Stone associate, and a case about a leak of CIA documents -- are still active.

The court chose to make public the documents in Assange's case Wednesday at the Justice Department's request.

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