US investigating release of classified docs on Israel's preparations for possible Iran strike

The documents, which are marked top secret, were posted to the Telegram messaging app last week and first reported by CNN and Axios. The AP first reported Sunday about the U.S. investigation into the unauthorized release, citing three U.S. officials. The AP said a fourth U.S. official, who also spoke on condition of anonymity, indicated that the documents appeared to be legitimate. 

House Speaker Mike Johnson, R-La., also confirmed the investigation in an appearance on CNN. 

"The leak is very concerning. There's some serious allegations being made, there's an investigation underway, and I'll get a briefing on that in a couple of hours," Johnson said Sunday on CNN's "State of the Union." "There's a classified level briefing and then another. But we're following it closely." 

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 by another method, like a hack - and whether any other intelligence information was compromised, one of the officials told the AP, adding that officials are working to determine who had access to the documents before they were posted. 

The documents are descriptions of satellite images showing Israeli warplanes preparing for a strike and practicing air refueling, according to officials. There is no information in the leaked documents about what the targets are or what Israeli plans to strike.

"These are NOT Israeli war plans for Iran," a senior U.S. defense official told Fox News.

In a statement to the AP, the Pentagon said it was aware of the reports of the documents but did not elaborate further. The AP said the Israeli military did not immediately return their request for comment.

Fox News' Jennifer Griffin and The Associated Press contributed to this report.