The FBI announced Tuesday it is investigating the alleged leak of highly classified documents that assess Israel's plans to attack Iran.
"The FBI is investigating the alleged leak of classified documents and working closely with our partners in the Department of Defense and Intelligence Community," the FBI wrote in a statement, The Washington Post reported. "As this is an ongoing investigation, we have no further comment."
White House national security spokesman John Kirby said Monday the administration was still not certain if the classified information that became publicly disclosed was leaked or hacked.
"We're not exactly sure how these documents found their way into the public domain," Kirby told reporters.
Former President Donald Trump said "the leaker" needs to be found because Israel "no longer wants to share documents with U.S."
"U.S. leaked highly confidential Documents from Israel. May have come from Defense Department. Israel has been seriously damaged and compromised by this. Wartime strategy and data. Probably came from Defense Department. MUST FIND THE LEAKER! Israel no longer wants to share documents with U.S., and who can blame them!" Trump posted Tuesday morning on Truth Social.
The documents appear to have been prepared by the National Geospatial-Intelligence Agency, describing U.S. interpretations of Israeli Air Force and Navy planning based on satellite imagery from Oct. 15-16.
They began circulating last week on the Telegram messaging app. Israel has been planning a response to a ballistic-missile barrage carried out by Iran on Oct. 1, Tehran's second direct attack on Israel in six months. Israel has intensified its offensive in Gaza and Lebanon, days after the killing of Hamas leader Yahya Sinwar.
House Speaker Mike Johnson, R-La., said Sunday an investigation regarding "the leak" was under way.
CNN reported last week that Israel was ready to launch its counterstrike against Iran in response to Tehran's recent missile barrage against the Jewish state, and it could happen before the Nov. 5 presidential election.
On Oct. 1, Iran fired a salvo of ballistic missiles at Israel in retaliation for Israel's campaign against Tehran's Hezbollah allies in Lebanon.
The Associated Press and Reuters contributed to this story.