The U.S. is investigating an unauthorized release of classified documents that assess Israel's plans to attack Iran, three U.S. officials told The Associated Press. A fourth U.S. official said the documents appear to be legitimate.

The documents are attributed to the U.S. Geospatial Intelligence Agency and National Security Agency and note that Israel continues to move 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 online to Telegram and first reported by CNN and Axios. The officials spoke on the condition of anonymity because they were not authorized to discuss the matter publicly.

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, one of the officials said. As part of that investigation, officials are working to determine who had access to the documents before they were posted, the official said.

The documents emerged as the U.S. has urged Israel to take advantage of its elimination of Hamas leader Yahya Sinwar and press for a ceasefire 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.

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