The White House urged journalists not to report on what appears to be leaked Pentagon classified documents circulating online.

John Kirby, the coordinator for Strategic Communications at the National Security Council, made his case during the White House press briefing on Monday as the U.S. government scrambles to respond to what some suggest may be the largest breach of classified secrets since the Edward Snowden saga.

“Without confirming the validity of the documents, this is information that has no business in the public domain,” Kirby said from the podium after facing repeated questions about the documents.

“It has no business — if you don’t mind me saying — on the front pages of newspapers or on television,” he added. “It is not intended for public consumption, and it should not be out there.”

The Pentagon released a statement on Sunday saying the Department of Defense (DoD) is working to assess the validity and national security impact of images that began popping up in recent weeks on social media, starting with Discord, showing what appears to be secret details about ChinaRussia’s war in Ukraine, surveillance efforts, and more. U.S. officials engaged with allies, partners, and Congress about the disclosure, the Pentagon added.

A U.S. defense official told The Washington Post many of the documents look like they were prepared for Gen. Mark Milley, chairman of the Joint Chiefs of Staff, and other senior military officials, but stressed these records would be available broadly to people with proper clearance.

The source of the apparent leak remains unclear, but the Department of Justice has opened a criminal investigation into the matter following a referral from the DoD. Kirby, a retired Navy rear admiral who previously served as Pentagon spokesman, confirmed there is suspicion that at least some of the images of documents may have been doctored.

On Sunday, Israel pushed back on alleged intelligence that said the country’s Mossad intelligence agency encouraged protests against Prime Minister Benjamin Netanyahu’s controversial judicial reforms plan. “The report that was published overnight in the American press is mendacious and without any foundation whatsoever,” said the prime minister’s office in a Twitter post it claimed was on Mossad’s behalf.

President Joe Biden is staying briefed on the situation, Kirby said on Monday. Asked whether the suspected leak is contained and whether there is an ongoing threat, Kirby said, “We don’t know. We truly don’t know.”