An apparent U.S. intelligence breach related to Israel’s plans to strike Iran has unsettled the intelligence community and sent the Biden administration scrambling to determine if it came from a hack or an internal leak.

The breach, first posted to the Telegram messaging app Friday, comes as the globe has been bracing for an Israeli retaliatory strike on Iran since Tehran fired some 180 ballistic missiles at Israel on Oct. 1 in response for the killings of top leaders in Hamas and Hezbollah, Iran’s prized proxies.

The FBI, aided by the Pentagon and intelligence agencies, is now investigating the unauthorized leak. Here’s what we know so far:

What was in the leak?

The leaked reports in question include one from the National Geospatial-Intelligence Agency, which analyzes satellite imagery, and one from the National Security Agency, which intercepts communications. Both were dated Oct. 16 and held highly classified information.

The documents were only meant to be viewed by the “Five Eyes” — the U.S. and its allies Australia, Canada, New Zealand and the United Kingdom.

Screenshots of the documents — first published on an Iran-linked Telegram account and circulated on social media — show descriptions of Israel’s possible plans for an attack on Iran, including the types of aircraft and munitions its military might use. The reports do not suggest Israel’s potential targets, but say a strike could come without forewarning.

The top-secret assessments detail U.S. tracking of Israeli airfield activity Oct. 15-16, to include the movement of munitions such as air-launched ballistic missiles and air-to-surface missiles.

The U.S. also observed an exercise “likely to practice air-to-air refueling and combat search and rescue operations with a large number of aircraft,” something that would be needed should Israeli fighter jets be used to strike Iran. 

White House response

The Biden administration quickly condemned the leak.

“We’re deeply concerned, and the president remains deeply concerned, about any leakage of classified information into the public domain,” White House national security spokesperson John Kirby told reporters Monday. 

“That is not supposed to happen, and it’s unacceptable when it does.”

Kirby also revealed that a Pentagon investigation was seeking to determine whether the documents were a hack or a leak. 

On Tuesday, the FBI revealed it had launched an investigation into the incident and was “working closely with our partners in the Department of Defense and Intelligence Community.”

The FBI’s involvement is notable given that it investigates violations of the Espionage Act, the U.S. law that makes it illegal to retain or disclose national defense information.

A U.S. official told The Associated Press the investigation also was meant to glean if other intelligence information was compromised, and who had access to the documents before they were posted.

Defense Secretary Lloyd Austin said Monday the U.S. military takes “these types of things very seriously, very, very seriously, and we investigate things if there is any type of incident.”

The administration appears shaken given the incident’s similarity to last year’s leaking of classified documents from the National Geospatial-Intelligence Agency by Jack Teixeira, an Air National Guard member from Massachusetts. 

Teixeira pleaded guilty in March to leaking hundreds of secret military documents about Russia’s war on Ukraine and other national defense information.

Pentagon pushes back on reports

The Pentagon on Tuesday declined to comment on its role in the probe but said that Austin has spoken with his Israeli counterpart about the matter.

“The investigation is in its first few days, so it’s important to let that investigation run its course,” press secretary Maj. Gen. Pat Ryder told reporters. 

The Pentagon also has denied allegations linking a specific Defense Department staffer to the leaks: Ariane Tabatabai, the chief of staff to Christopher Maier, the assistant secretary of Defense for special operations and low-intensity conflict.

Foreign outlets have circulated reports that she is to blame, but Ryder denied her culpability. 

“To my knowledge, this official is not a subject of interest, and the department remains fully committed to supporting the investigation,” he said.

GOP quick with criticism

Republican politicians quickly jumped on the leak, while former President Trump added his voice to the fray Tuesday when he suggested without evidence that “enemies from within” were responsible for the breach.

“They leaked all the information about the way that Israel’s going to fight and how they are going to fight and where they are going to go,” Trump said Tuesday at a campaign event focused on Latino leaders.

“Can you imagine somebody doing that? That’s the enemy. I guess that maybe is the enemy from within, as I talked about,” he added. 

“We just can’t stand for this incompetence anymore.”

House Speaker Mike Johnson (R-La.) on Sunday said he was alarmed by the incident.

“The leak is very concerning. There’s some serious allegations being made there, an investigation underway, and I’ll get a briefing on that in a couple of hours,” Johnson said on CNN’s “State of the Union.”

And Rep. Brian Mast (R-Fla.) warned that the United States needs to deal with its “leaky ships” and that the Israel intelligence leak should be considered an “act of treason.”

Israel’s looming retaliation

Israel is expected to launch a retaliatory strike on Iran following Tehran’s missile barrage on the country earlier this month, which was in response to the killings of Hamas leader Ismail Haniyeh in Tehran in July and Hezbollah chief Hassan Nasrallah in Beirut in September. 

Washington has been trying to steer its ally away from striking Iranian nuclear or oil sites, as U.S. officials fear such a move could further inflame the region on top of Israel’s war against Hamas in the Gaza Strip and against Hezbollah in Lebanon.    

The intelligence leak comes after Israel killed Hamas leader Yahya Sinwar, the mastermind of the Oct. 7, 2023, attack on Israel, during which Hamas soldiers killed more than 1,200 civilians and set off the Gaza war. 

President Biden and Vice President Harris are now calling for a cease-fire to end the conflict and release the hostages still in Hamas captivity.