▶ Watch Video: White House says it doesn’t know if Pentagon documents leak is contained

The Biden administration is trying to manage the fallout from leaked classified intelligence documents that started circulating online in the past week. 

Photos of pages of paper documents that appear to have been unfolded have appeared on social media, and some of the materials contain details from daily updates provided to senior leaders at the Pentagon about operations in Ukraine, as well as other intelligence updates, according to a Pentagon official.  

CBS News has reviewed a number of slides so far, as the U.S. government continues to try to remove them from social media. Some include graphics and maps of the state of Russia’s war in Ukraine as of March. Others depict combat sustainability assessments and an analysis of Ukraine’s air defenses. 

Asked by reporters Monday if the threat to national security has been contained, National Security Council spokesperson John Kirby responded, “We don’t know. We truly don’t know.” 

The Biden administration is not yet sure how extensive the document leak is, and still doesn’t know who is behind it. The Justice Department, at the request of the Defense Department, has opened a criminal investigation

The Pentagon has not verified that the photos of the documents are authentic, and officials noted that some of them appeared to be doctored. But they also confirmed that some of the slides do appear to contain secret information.

Chris Meagher, assistant to the defense secretary for public affairs, told reporters Monday the “photos appear to show documents similar in format to those used to provide daily updates to our senior leaders on Ukraine and Russia related operations, as well as other intelligence updates.” 

“A Pentagon team continues to review and assess the veracity of the photograph documents that are circulating on social media sites and that appear in some cases to contain sensitive and highly classified material,” Meagher said. 

Meagher declined to confirm the authenticity of specific documents. But Kirby said at least a portion of the material appeared to be altered.

“We know that some of them have been doctored,” Kirby said. “I won’t speak to the validity of all the documents, the ones that don’t immediately appear to be doctored. We’re still working through the validity of all the documents that we know are out there.” 

The Pentagon is leading an interagency effort to look at the impact of the leak on U.S. national security and on the United States’ allies. 

Kirby said the president has been briefed on the leak, and was updated throughout  the weekend. Defense Secretary Lloyd Austin has been speaking with senior leaders daily about the unauthorized disclosures, Meagher said Monday. 

For now, the administration is being cautious about what it says about the leak publicly. 

“I think we just need to be careful right now speculating or guessing what might be behind or who might be behind what looks like a potential leak here of classified information,” Kirby said. “We need to let the process sort of bear itself out.”