The attorney general said the 21-year-old was arrested in Massachusetts without incident and would be arraigned in federal court there.
A Massachusetts air national guardsman, Jack Teixeira has been arrested for allegedly leaking classified documents.
The United States Federal Bureau of Investigation (FBI) arrested Teixeira on Thursday.
The number of documents leaked is reportedly over 100 and is believed to be the most serious security breach in years.
Addressing a press conference on Thursday, US Attorney General, Merrick Garland, said the leaked documents included detailed intelligence assessments of the US allies and adversaries.
Garland added that the documents posted in an online group by the suspect also included the state of the war in Ukraine and the challenges Kyiv and Moscow face.
He disclosed that Teixeira was arrested on Thursday “in connection with an investigation into alleged unauthorized removal, retention, and transmission of classified national defense information”.
The attorney general said the 21-year-old was arrested in Massachusetts without incident and would be arraigned in federal court there.
“This investigation is ongoing. We will share more information at the appropriate time,” Garland said.
The New York Times reports that Teixeira led an online group where about 20 to 30 people shared their love of guns, racist memes, and video games.
President Joe Biden said he was not bothered about the details of the document, but by the fact that the leaks happened.
“I’m not concerned about the leak. I’m concerned that it happened, but there’s nothing contemporaneous that I’m aware of that is of any consequence,” he said.
It is understood that the Pentagon is now taking steps to whittle down its list of who receives highly classified intelligence briefs following the leak.