AUGUSTA — Sen. Angus King and colleagues on the Senate intelligence committee grilled members of the Trump administration Tuesday about a report that more than a dozen high-ranking officials used a messaging app to text each other about detailed plans for a military attack in Yemen this month.

The chat was not secure and a journalist was invited to join, apparently by mistake.

The administration confirmed a report from Jeffrey Goldberg, editor-in-chief of The Atlantic magazine, that he was added to the text chain on the encrypted messaging platform, Signal, by someone who works for National Security Adviser Mike Waltz. The participants apparently did not know a journalist was part of the chat.

The chain included Vice President JD Vance, Defense Secretary Pete Hegseth and Secretary of State Marco Rubio, among others, and included details of the planned attack two hours before it occurred. The revelation prompted outrage and calls for an investigation.

Democratic senators and King, an independent who caucuses with Democrats, used a previously planned hearing of the Senate Select Committee on Intelligence to demand answers about the security breach and challenge the administration’s efforts to downplay it.

While Republican Chairman Sen. Tom Cotton of Arkansas commended the administration for the attack against Houthi rebels in Syria, Democratic Vice Chairman Mark Warner of Virginia railed against the use of Signal to plan the attack.

Warner called it “sloppy, careless, incompetent behavior” that would have gotten anyone else fired. He said that it was “mind-boggling” that those on the chat didn’t know who was on the message chain.

The senators pressed Tulsi Gabbard, the director of national intelligence and the administration official who oversees the protection of classified information.

During the sometimes-tense hearing, Gabbard would not answer questions about whether she was part of the chat while at the same time she repeatedly told King and other senators that nothing shared in the text chain was classified information. “There was no classified information that was on the Signal chat,” she said.

King questioned Gabbard about how it’s possible that sensitive information such as attack sequences, timing, weapons and targets would not be classified. Gabbard said she would “defer to the secretary of defense and the National Security Council,” prompting a rebuke from King.

“You’re the head of the intelligence community. You’re supposed to know about classifications,” King said. “So your testimony here today is very clearly that nothing that was in that set of texts were classified. … If that’s the case, then please release that whole text stream so that the public can have a view of what actually transpired on this discussion. It’s hard for me to believe that targets and timing and weapons would not have been classified.”

In addition to Gabbard, FBI Director Kash Patel and CIA Director John Ratcliffe were among those testifying before the committee to discuss global threats, which included countering the deadly drug fentanyl and fighting violent crime, human trafficking and illegal immigration.

Sen. Susan Collins, a senior Republican who also serves on the committee, told reporters in Washington, D.C., that the incident was “inconceivable” and  “extremely troubling and serious.”

Collins did not attend the hearing because of an illness, her office said. She was well enough to cast floor votes later in the day, aides said.

Collins said in a written statement later Tuesday that she planned to submit formal questions to Gabbard and Ratcliffe, and was looking forward to the National Security Council’s review.

“As a member of the Senate Intelligence Committee, I receive frequent classified briefings on global threats and military operations,” Collins said. “From the information available to me at this time, the consequences of this group chat could have been egregious and far-reaching, or even posed a threat to our service members and our national security. I’m seeking more information, including why and how this even happened.”

When asked about the report on Monday, President Donald Trump said he did not know anything about it. On Tuesday, he stood by the embattled adviser whose office invited the journalist to the chat and said the chat had “no impact at all” on the operation.

“Michael Waltz has learned a lesson, and he’s a good man,” Trump reportedly said Tuesday in a phone interview with NBC News.

Trump was sharply critical of former Secretary of State Hillary Clinton’s use of a private email server during their 2016 presidential race. He also was charged with illegally taking classified information after losing the 2020 election, although that case was dropped when he was reelected.

Goldberg said he was added to the text chain days before the attack.

At first, Goldberg said he questioned whether the other participants were in fact part of the administration and that it wasn’t a hoax, but as time went on and the attacks were actually  carried out, he realized it was authentic. He did not report on the details of the text chain until after the attack, which killed at least 53 people. And even then, he withheld some information because he was concerned about compromising U.S. intelligence sources.

Rep. Jared Golden, D-2nd District, criticized the security lapse in a written statement Monday night, saying that senior administration officials should be held to the same standard as enlisted soldiers, who could face a court martial or discharge for leaking information before an attack.

“This is a clear failure of information security that could have had grave consequences for the United States, our men and women in uniform, and our allies,” Golden said. “We’re lucky the journalist involved acted responsibly, but this incident raises questions about communications practices at the highest levels of the national security apparatus. If a service member acted this carelessly with such sensitive information they would face serious consequences, including the potential loss of security clearance, court martial or discharge. These officials should be held to the same high standard.”

And Rep. Chellie Pingree, D-1st District, said in a social media post that the officials “may have violated the Espionage Act and federal records laws. Pingree was “stunned by the staggering incompetence and jaw-dropping recklessness revealed in the reporting.”

“This level of carelessness from the highest levels of government should alarm every American, regardless of political party,” Pingree said. “There must be a full investigation, not only into this incident, but also into how the Trump administration is communicating classified information more broadly.”