Army Gen. Daniel R. Hokanson, chief of the National Guard Bureau, engages with airmen at Muñiz Air National Guard Base, Carolina, Puerto Rico, on Feb. 5, 2023. (Rafael D. Rosa/U.S. Air National Guard)

WASHINGTON — The chief of the National Guard Bureau on Thursday assured lawmakers that the monthslong leak of classified military documents by a Massachusetts Air National Guard member was an individual act that will never be repeated.

Army Gen. Daniel Hokanson told members of the Senate Appropriations Committee that the National Guard will put in place safeguards to prevent the kind of breach that allowed 21-year-old Airman 1st Class Jack Teixeira to access and share some of the nation’s most secret information.

“I’m very confident this will never happen again,” Hokanson said. “This one individual took an individual action and is not indicative of the entire system.”

Hokanson promised to implement recommendations immediately from multiple investigations into the leak, including a probe by the Air Force’s inspector general that is nearly completed.

Senators were not entirely satisfied with that vow, noting Teixeira had raised suspicion within the National Guard long before he was arrested in April for posting on social media classified intelligence on the war in Ukraine and other sensitive national security issues.

Court documents released last month showed Teixeira had been admonished by supervisors at least twice over “concerning actions” that he took with classified information.

“This was not a deviation that came out of the blue, but in fact he had been reprimanded and he had been instructed to ’stop any deep dives into classified intelligence information and focus on his job,’ ” Sen. Susan Collins, R-Maine, said, quoting from an Air National Guard 102nd Intelligence Wing memo. “These reports are very concerning because it appears that this serious breach might have been prevented or stopped much sooner.”

Hokanson said multiple investigations are looking into Teixeira’s chain of command and several people have been temporarily removed from their posts while the probes are underway. Teixeira served in cyber defense operations at Otis Air National Guard Base in Massachusetts and was working for a combatant commander at the time of the leaks, Hokanson said.

“If there was negligence on [the commanders’] part, it will be addressed immediately,” he said.

Senators said Thursday that they will continue to press for accountability and reforms after the investigations are wrapped up. Sen. Jon Tester, D-Mont., the chairman of the committee’s defense subpanel, said the leak has negatively affected the reputation of the Air National Guard.

Teixeira is accused of violating the Espionage Act and remains in custody awaiting trial. He could face up to 15 years in prison if convicted and has not yet entered a plea.