WASHINGTON >> The top Republican and Democrat on the Senate Armed Services Committee requested an investigation Thursday into how Trump administration national security officials used the Signal messaging app to discuss U.S. military strikes on Yemen, with an inadvertent leak to a national journalist.

And a federal judge said he would order the preservation of the messages, ensuring at least some scrutiny on an episode President Donald Trump has dismissed as frivolous.

Meanwhile, the Justice Department, which has traditionally handled investigations into the mishandling of classified or sensitive information by both Republican and Democratic administrations, showed that under Trump it would likely stay on the sidelines.

Sen. Roger Wicker, the Republican chair of the committee, and Sen. Jack Reed, the top Democrat, signed onto a letter to the acting inspector general at the Department of Defense for an inquiry into the potential “use of unclassified networks to discuss sensitive and classified information, as well as the sharing of such information with those who do not have proper clearance and need to know.”

The senators’ assertion that classified information was potentially shared was notable, especially as Trump’s Republican administration has contended there was no classified information on the Signal chain that had included Jeffrey Goldberg, editor-in-chief of The Atlantic magazine, who broke the story Monday.

Later Thursday, U.S. District Judge James Boasberg said during a hearing for a lawsuit brought by a nonprofit watchdog, American Oversight, that he’ll issue a temporary restraining order barring administration officials from destroying the messages.

First major test

Across Washington, the Signal leak presented a major test early in Trump’s second term on the federal government’s system of checks and balances meant to protect national security. Yet even as mechanisms for oversight and investigation sputtered to life, most Republicans in Congress seemed content to allow the controversy to blow over.

Meanwhile, Democrats slammed the Signal chat as a reckless violation of secrecy that could have put service members in harm’s way.

“This put pilots at risk because of sloppiness and carelessness,” said Sen. Mark Kelly, an Arizona Democrat and former fighter pilot.

Kelly and other Democrats have called for Defense Secretary Pete Hegseth to either resign or be fired. “If this was an officer in the military — at any level — or enlisted person, they would have been fired already,” Kelly said.

Hegseth was on the chat stream along with other top administration officials.

Asked by a reporter Wednesday about the call by Wicker, of Mississippi, and Reed, of Rhode Island, for an investigation, Trump replied, “It doesn’t bother me.”

Classified hearing requested

Wicker, whose support was crucial to Hegseth’s Senate confirmation, is one of the most ardent defense hawks in Congress and has said the committee will request a classified hearing to follow up on the inspector general’s report, as well as for the administration to verify the contents of the Signal chat. The contents, which were published by The Atlantic, show that Hegseth listed weapons systems and a timeline for the attack on Iran-backed Houthi rebels in Yemen earlier this month.

Senate Republicans have criticized the discussion on Signal but have stopped short of calling for the removal of Hegseth or anyone else involved. Sen. Mike Rounds, a Republican member of both the Senate Intelligence and Armed Services committees, said any oversight should be done “in a bipartisan way.”

Still, Democrats are pressing to probe much deeper. Sen. Mark Warner, the top Democrat on the Senate Intelligence Committee, said he wants to check the phones of those involved in the Signal chat for malware as well as whether Hegseth had shared military plans on other Signal chats.

Warner said he expected support from Republicans in calling for such an investigation, but so far Warner’s Republican counterpart on the intelligence committee, Sen. Tom Cotton, has given no sign he would join in those calls.

Justice Department view

When asked at an unrelated news conference what the Justice Department plans to do, Attorney General Pam Bondi deflected, saying the mission in Yemen was ultimately a success.

Echoing the White House, Bondi also insisted that none of the information shared on Signal was classified, even though officials have provided no evidence that that’s the case. Espionage Act statutes require the safe handling of closely held national defense information even if it’s not marked classified.

Bondi, who has pledged not to play politics with the department, quickly pivoted to former Secretary of State Hillary Clinton and former President Joe Biden, who were investigated for allegations that they mishandled classified information but were not charged. Both Democrats were subject to extensive criminal investigations, and the FBI and the Justice Department have long track records of such inquiries.

Order to preserve files

Also Thursday, District Judge Boasberg ordered the Trump administration to preserve records of chat, barring administration officials from destroying any messages..

The nonprofit watchdog, American Oversight, requested the order. A government attorney said the administration already was taking steps to collect and save the messages.

American Oversight sued this week to ensure that the records are kept in accordance with the Federal Records Act. The group suspects that administration officials routinely use Signal to communicate.

“Defendants’ use of a non-classified commercial application even for such life-and-death matters as planning a military operation leads to the inevitable inference that Defendants must have used Signal to conduct other official government business,” American Oversight’s attorneys wrote in a court filing.

Boasberg limited his order to messages sent between March 11 and March 15.

“I’m glad we could figure out a solution,” the judge later said. He instructed the government to provide him with an update Monday. Boasberg said his order will expire April 10 “in the event that Defendants’ measures are satisfactory to the Court.”

Boasberg, chief judge of the district court in Washington, has been at odds with the administration over a separate case involving flights deporting Venezuelan immigrants to El Salvador under an 18th century wartime law.

National Security Council

Meanwhile, the White House National Security Council has also said it would investigate the Signal chat. White House press secretary Karoline Leavitt told reporters on Thursday that she had no update on the status of that investigation.

“We’ve been incredibly transparent about this entire situation, and we will continue to be,” Leavitt said.