An Air National Guardsman suspected of leaking highly classified U.S. documents will be arrested on Thursday in Massachusetts, a source familiar with the situation told Reuters.
The source, who spoke on condition of anonymity, did not elaborate. The FBI did not immediately respond to a request for comment on developments in the investigation.
The Department of Justice opened a formal criminal probe last week and the Pentagon is assessing the damage done by what may be the most damaging release of classified U.S. information in years.
The New York Times reported that the leader of an online group where the secret documents were posted is a member of the Massachusetts Air National Guard.
Named Jack Teixeira, the national guardsman led Thug Shaker Central, an online group where about 20 to 30 people shared their love of guns, racist memes and video games, the Times said, citing interviews and documents it reviewed.
U.S. President Joe Biden earlier on Thursday said investigators were closing in on the source of the leak.