Secretary of Defense Lloyd Austin vowed the Pentagon will "turn over every rock" in its investigation into the leak of dozens of classified documents on social media.

The Pentagon has launched a "cross-department effort" that includes the public affairs office, legislative affairs team, the general counsel's office, joint staff, and others to probe the source of the leak and its wide-ranging ramifications, Chris Meagher, assistant to the secretary of defense for public affairs, told reporters on Monday.

WHAT WE KNOW ABOUT THE PENTAGON LEAKS AND WHAT WE DON'T

Many details of the leak remain unanswered, including the culprit, how he or she accessed the documents, the amount of information that has been released, and whether more is coming. The Pentagon has also referred the matter to the Department of Justice, which opened a criminal investigation.

"I will tell you that we take this very seriously," Austin said on Tuesday in his first public remarks since the leak was discovered. "And we will continue to investigate and turn over every rock until we find the source of this and the extent of it."

The secretary said he was made aware of the leak on April 6 and has convened military leaders for daily updates since the 7th. The documents the department "is aware of are dated the 28th of February and the first of March," Austin added, noting, "I don't know if there are other documents that have been online before, and these are things that we will find out as we continue to investigate."

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The released documents, not intended for public consumption, provide insight into the U.S. intelligence community's reach and its apparent willingness to spy on allies, though their veracity is unclear given some have purportedly been altered or manipulated. Officials from South Korea, Ukraine, and the United Kingdom have said some of the released documents appear to be fake or changed.

One document, for example, appeared to show Russia and Ukraine's casualty totals for the war, only for a subsequent photo to appear online showing distorted casualty numbers that favor Russia. Ukrainian presidential adviser Mykhailo Podolyak said the posts looked like a Russian disinformation operation.