President Joe Biden is “deeply concerned” about the release of classified documents on Israel's preparation for a potential retaliatory attack on Iran, according to a White House spokesman.

U.S. officials confirmed on Saturday that the administration is investigating an unauthorized release of classified documents that assess Israel’s plans to attack Iran.

White House national security spokesman John Kirby said on Monday that the administration was still not certain if the classified information that became publicly disclosed was leaked or hacked.

Kirby added that administration officials don’t have any indication at this point of "additional documents like this finding their way into the public domain.” He added the Pentagon is investing the matter.

“We’re deeply concerned and the president remains deeply concerned about any leakage of classified information into the public domain. That is not supposed to happen and it’s unacceptable when it does,” Kirby said.

The documents are attributed to the National Geospatial-Intelligence Agency and National Security Agency, and note that Israel was still moving military assets in place to conduct a military strike in response to Iran’s blistering ballistic missile attack on Oct. 1. They were sharable within the “Five Eyes,” which are the U.S., Great Britain, Canada, New Zealand and Australia.

The documents, which are marked top secret, were posted to the Telegram messaging app.