(NewsNation) — The Pentagon is rushing to contain the fallout from a massive leak of classified documents that reveal critical information about U.S. allies and the war in Ukraine.

The source of the leak is unclear and has raised intelligence concerns that the breach may erode allies’ trust in sharing information with the U.S.

“They were somewhere in the web, and where exactly, and who had access at that point, we don’t know. We simply don’t know,” Defense Secretary Lloyd Austin said at a news conference Tuesday. “We will continue to investigate and turn over every rock until we find the source of this and the extent of it.”

The leaks have highlighted how closely the U.S. tracks how its allies interact with Russia and China. Former Defense Secretary William Cohen described the leaked information as “critical to our national security.”

“In addition to classifying and overclassifying, the security has become lax. We have become sloppy,” Cohen told NewsNation host Elizabeth Vargas. “We’ve had former presidents who have taken documents after they’ve left office. We’ve had a former vice president – the same thing. President Joe Biden, also. So we’ve become pretty lackadaisical in terms of maintaining the security.”

The Washington Post reported that the leaks revealed that Egypt’s president ordered subordinates to secretly prepare to ship up to 40,000 rockets to Russia during the war with Ukraine. An Egyptian foreign ministry spokesperson insists they are maintaining “noninvolvement in this crisis and committing to maintain equal distance with both sides.”

“This is embarrassing to be sure. It’s serious, and it could possibly be fatal depending upon was this based on human intelligence, can the Russians and others go back and re-engineer this so they can figure out who’s leaking information on their side, and how’s it getting to the U.S. in our documents,” Cohen questioned.

Cohen believes the leak could possibly leave people informing the U.S. in a dangerous situation.

“We rely upon human intelligence. From the very beginning, when Putin went into Ukraine, we were seeing information coming out projecting what Putin was going to do. Many of us, including myself, are on television saying Putin has a problem. He’s got a mole or many moles inside of his intelligence community, and he doesn’t know where it’s coming from,” Cohen said. “So to the extent this is leaked, and they can trace it back to who it is, then that person has a choice of either running for his life with staying put and seeing if the KGB or successor tracks him down.”

An internal review is underway by the Pentagon to analyze the leak’s impact on national security. Senior military officials are reaching out to allies about the leak.

“People’s lives are at stake when we hire people or get people to spy for us. Their lives are on the line for us (…) When we have leaks like this, they’re in danger and our credibility is put in question,” Cohen said.

Cohen says it will be a difficult order to track down the source of the breach.

The Associated Press contributed to this report.