The United States is investigating a reported unauthorized release of classified documents that assess Israel’s plans to attack Iran, a U.S. defense official confirmed to CBS News.

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., Britain, Canada, New Zealand and Australia.

The documents, which are marked top secret, were posted to the Telegram messaging app and first reported on Saturday by CNN and Axios.

House Speaker Mike Johnson, speaking on CNN’s “State of the Union” on Sunday, confirmed that an investigation is underway.

“There’s a classified-level briefing … we are following it closely,” he said, not providing any additional details on the briefing.

The White House said it was not commenting on the purported leak, despite Johnson’s confirmation of an investigation, and directed CBS News’ questions to the Department of Justice.

Spokespeople for the National Geospatial-Intelligence Agency and the FBI declined to comment. A U.S. official told the Associated Press that the documents appear to be legitimate.

The investigation is also examining how the documents were obtained — including whether it was an intentional leak by a member of the U.S. intelligence community or obtained by another method, like a hack — and whether any other intelligence information was compromised, a U.S. official told the AP. As part of that investigation, officials are working to determine who had access to the documents before they were posted, the official said.

In a statement, the Pentagon said it was aware of the reports of the documents but did not have further comment.

The Israeli military did not immediately respond to a request for comment over the leak of the two documents.

The documents first appeared online Friday via a channel on Telegram, claiming they had been leaked by someone in the U.S. intelligence community, then later the U.S. Defense Department. The information appeared entirely gathered through the use of satellite image analysis.

One of the two documents resembled the style of other material from the National Geospatial-Intelligence Agency leaked by Jack Teixeira, an Air National Guardsman who pleaded guilty in March to leaking highly classified military documents about Russia’s war on Ukraine and other national security secrets.

The Telegram channel involved in the leak identifies itself as being based in Tehran, Iran’s capital. It previously published memes featuring Iran’s Supreme Leader Ayatollah Ali Khamenei and material in support of Tehran’s self-described “Axis of Resistance,” which includes Middle East militant groups armed by the Islamic Republic.

The U.S. has urged Israel to take advantage of its elimination of Hamas leader Yahya Sinwar and press for a cease-fire in Gaza, and has likewise urgently cautioned Israel not to further expand military operations in the north in Lebanon and risk a wider regional war. However, Israel’s leadership has repeatedly stressed it will not let Iran’s missile attack go unanswered.

contributed to this report.