The U.S. does not yet know whether the full extent of leaked Pentagon documents has been made public, the White House announced Monday.

National Security Council spokesman John Kirby made the announcement during a press briefing at the White House on Monday, telling reporters that the investigation was ongoing and few conclusions have been made. Multiple classified documents have leaked online in recent weeks, purporting to detail U.S. assessments of Ukraine and other things.

Kirby confirmed that President Biden has been briefed on the issue and continues to be kept up-to-date on the investigation. The Pentagon referred the matter to the Justice Department for criminal investigation.

"Does the U.S. government at this point have any sense of who was behind [the leak]?" a reporter asked.

LEAKED PENTAGON DOCUMENTS PAINT GRIM PICTURE OF UKRAINIAN AIR DEFENSE SUPPLIES, MAY ONLY LAST A MONTH

National Security Council spokesman John Kirby

National Security Council spokesman John Kirby told reporters that the U.S. does not know whether more leaked Pentagon documents will come to light in the coming days. (AP Photo/Susan Walsh)

An aerial photo of the Pentagon

The Department of Defense suffered a seemingly extensive leak last week after classified documents began circulating online, detailing U.S. communications and assessments of allies. (STAFF/AFP via Getty Images)

"As you know, the Department of Defense has referred this to the Department of Justice for a criminal investigation. I certainly would refer you to them, but I'm not aware that they've come to any conclusions about where [the leaks] are coming from," Kirby responded.

"At this point, do you believe the leak is contained? Are there more documents out there that have not yet been released publicly? Is this an ongoing threat?" the reporter pressed.

"We don't know," Kirby responded. "We truly don't."

UKRAINE WAR PLANNING DOCUMENTS LEAKED ONLINE, PENTAGON INVESTIGATING

The Pentagon said on Sunday that an interagency task force is assessing the validity and impacts of the "sensitive and highly classified material" that has leaked online.

The leaked documents pertain to a wide range of issues and countries, detailing one instance in which a British spy plane was nearly shot down by a Russian jet off the coast of Crimea last year. U.K. Defense Minister Ben Wallace previously told the British Parliament that the Russian jets flew "recklessly," but chalked the missile launch up to a "technical malfunction."

The leaks also suggested that Israel's intelligence agency, the Mossad, had secretly encouraged the mass protests against Israeli Prime Minister Benjamin Netanyahu last month.

Benjamin Netanyahu

Leaks from the Pentagon suggested that the Mossad had supported protests against Israeli Prime Minister Benjamin Netanyahu, though his office denied the reports. (Mark Kerrison/In Pictures via Getty Images)

It alleged that Mossad "advocated for Mossad officials and Israeli citizens to protest the new Israeli Government’s proposed judicial reforms, including several explicit calls to action that decried the Israeli government, according to signals intelligence."

Netanyahu's office, which is in charge of Mossad, dismissed the claims in a statement to Fox News Digital.

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"The report that was published overnight in the American press is mendacious and without any foundation whatsoever. The Mossad and its senior officials did not — and do not — encourage agency personnel to join the demonstrations against the government, political demonstrations or any political activity," the prime minister's office wrote on behalf of the Mossad.