The first leak to Discord appeared to come less than 48 hours into Russia’s invasion of Ukraine in February 2022.Credit…Tyler Hicks/The New York Times

The Air National Guardsman accused of leaking classified documents to a small group of gamers had been posting sensitive information months earlier than previously known and to a much larger chat group, according to online postings reviewed by The New York Times.

In February 2022, soon after the invasion of Ukraine, a user profile matching that of Airman Jack Teixeira began posting secret intelligence on the Russian war effort on a previously undisclosed chat group on Discord, a social media platform popular among gamers. The chat group contained about 600 members.

The case against Airman Teixeira, 21, who was arrested on April 13, pertains to the leaking of classified documents on another Discord group of about 50 members, called Thug Shaker Central. There, he began posting sensitive information in October 2022, members of the group told The Times. His job as an information technology specialist at an Air Force base in Massachusetts gave him top secret clearance.

It is not clear whether authorities are aware of the classified material posted on this additional Discord chat group.

The newly discovered information posted on the larger chat group included details about Russian and Ukrainian casualties, activities of Moscow’s spy agencies and updates on aid being provided to Ukraine. The user claimed to be posting information from the National Security Agency, the Central Intelligence Agency and other intelligence agencies.

The additional information raises questions about why authorities did not discover the leaks sooner, particularly since hundreds more people would have been able to see the posts.

The exposure of some of America’s most closely guarded secrets has prompted criticism about how the Pentagon and intelligence agencies protect classified data, and whether there are weaknesses in both vetting people for security clearances and enforcing the mantra that access to secrets should only be given to people with a “need to know.”

The Times learned about the larger chat room from a Discord user. Unlike Thug Shaker Central, the second chat room was publicly listed on a YouTube channel and was easily accessed in seconds.

A chain of digital evidence collected by The Times ties the posts containing the sensitive information to Airman Teixeira. The posts were made under a user name that The Times has previously connected to Airman Teixeira. The person leaking the information said he worked at a U.S. Air Force intelligence unit. Details in videos and photographs he posted matched images posted by family members inside the Teixeira home in North Dighton, Mass. Fellow Discord members sent the user birthday wishes on Dec. 21, the same date Airman Teixeira’s sister wished him a happy birthday on Facebook. And he posted a photograph of an antique German rifle for which The Times found an online receipt in Airman Teixeira’s name.

The posts reviewed by The Times appear to be detailed written accounts of the classified documents themselves, and identify which intelligence agency they are from. While it appears that the user likely posted pictures of some documents, those have since been deleted from the chat group.

Joshua Hanye, one of Airman Teixeira’s attorneys from the Boston public defenders office, declined to comment about the latest revelations. Officials from the Federal Bureau of Investigation and the Justice Department also declined to comment.

It appears the first leak came less than 48 hours into Russia’s invasion of Ukraine. “Saw a pentagon report saying that ⅓rd of the force is being used to invade,” the user wrote. Apparently eager to impress others in the group who questioned his analysis, he said: “I have a little more than open source info. Perks of being in a USAF intel unit,” referring to the United States Air Force.

Some of the intelligence posted appeared to foretell battlefield developments. On March 27, 2022, he shared classified information about the Russian pullback from Kyiv, information he said he “found on an NSA site.”

“Some ‘big’ news,” he wrote. “There may be a planned withdrawal of the troops west of Kiev, as in all of them.” Two days later, Russian officials announced they were pulling back from the Ukrainian capital.

Some posts began with an update on casualty numbers. He also reported on Ukraine’s targeting priorities and the activities of Russian intelligence agencies. He took particular interest in posting updates of which countries were providing lethal aid to Ukraine.

At times, he appeared to be posting from the military base where he was stationed. In one conversation, he said he was about to enter an area where people with security clearance can access classified computer networks, known as a SCIF — Sensitive Compartmented Information Facility.

How Airman Teixeira obtained the documents that he is accused of posting online has been a key question for investigators. They believe he used administrator privileges connected to his information technology job to access documents. In his posts, Airman Teixeira said his job gave him access to material that others could not see. “The job I have lets me get privilege’s above most intel guys,” he wrote.

Airman Teixeira also claimed that he was actively combing classified computer networks for material on the Ukraine war. When one of the Discord users urged him not to abuse his access to classified intelligence, Teixeira replied: “too late.”

At one point he offered to share information privately with members of the group living outside the United States. “DM me and I can tell you what I have,” he wrote.

On another occasion, he wrote that he was able to access a site run by the National Security Agency, the U.S. spy agency that focuses on communications intercepted from computer networks, to look for updates on the war.

He also claimed to have access to intelligence from U.S. partners. “I usually work with GCHQ people when I’m looking at foreign countries,” he told the chat group in September 2022, referring to Government Communications Headquarters, the British agency for intelligence, security and cyberaffairs.

A spokesman for the National Security Agency declined to comment, referring questions to the Justice Department. A spokeswoman for the British Embassy declined to comment as well.

Airman Teixeira continued to share more detailed information to the larger chat group until a month ago.

“I was very happy and willing and enthusiastic to have covered this event for the past year and share with all of you something that not many people get to see,” he wrote on March 19, before adding, “I’ve decided to stop with the updates.”

Glenn Thrush, Ishaan Jhaveri and Riley Mellen contributed reporting.

Jack Teixeira, the Air National Guardsman accused of releasing classified material, in a photo posted on social media.Credit…Reuters

WASHINGTON — Jack Teixeira, a Massachusetts Air National Guardsman accused of posting classified documents about the war in Ukraine on social media, is expected to remain in custody for two weeks to give his court-appointed lawyer time to prepare his defense.

A detention hearing for Mr. Teixeira, who was arrested April 13 on two separate counts related to the unauthorized handling and publication of classified materials, had been scheduled for federal court in Boston on Wednesday. But his lawyer, Brendan Kelley, requested more time to address the government’s arguments, and the magistrate judge, David. H. Hennessey, quickly agreed.

Mr. Teixeira, 21, made a brief appearance in court on Wednesday to waive his right to a preliminary hearing. Dressed in an orange shirt and pants, he appeared subdued and made little eye contact.

Prosecutors often reveal new details of their case at detention hearings, but only enough information to argue that the defendant is a potential flight risk or poses a danger to national security if released.

The Justice Department did not object to the delay, which gives prosecutors more time to prepare its evidence for the more consequential step — an indictment before a grand jury — and to sort out logistics, like whether to request a potential change of venue closer to Washington, in Virginia.

Here’s what we know about the case against Airman Teixeira.

Neither prosecutors nor national security officials yet know the full extent of the intelligence taken from the U.S. government’s classified systems. The material posted online primarily includes slides about the war in Ukraine created by the intelligence directorate of the Pentagon’s Joint Staff. But there is also highly classified material from the National Security Agency, the Central Intelligence Agency, the Defense Intelligence Agency and other spy agencies.

Many of the dozens of documents that have emerged so far are snapshots in time — bits of intelligence or overviews of the battlefield in Ukraine compiled on a particular day. But some of the material provides a level of detail about the strengths and weaknesses of the Russian and Ukrainian forces that American officials have been reluctant to discuss.

The documents were first posted to Thug Shaker Central, a small group on Discord, a social media platform popular among gamers. They were later shared more widely, and some were altered and reposted on other social media.

Although the charges against Airman Teixeira pertain to the documents released to Thug Shaker Central, an investigation by The New York Times found that he apparently shared sensitive intelligence to a larger group on Discord months before that.

Airman Teixeira worked as an information technology specialist and had administrative privileges on classified computer systems that appear to have allowed him access to a wide range of material, including briefing slides. But investigators are also trying to learn if he might have collected the material using less technologically sophisticated methods. Officials caution that the inquiry is in early stages and there is more to learn about how the airman might have gathered the material and removed it from the military base where he worked.

The answer to that question will depend somewhat on what investigators learn about how he got access to this material. For now, intelligence agencies are not curbing their sharing of documents with the Pentagon. President Biden has ordered the Pentagon to limit the distribution of sensitive information, however. The Pentagon has also announced that it would review procedures across the Defense Department for using and securing the nation’s secrets.

Both the F.B.I. and news reporters found him in much the same way: by interviewing other members of Discord.

The members of the Thug Shaker Central Discord server who spoke with The New York Times did not reveal Airman Teixeira’s identity. But they shared some details about him, and reporters were able to find people on other video game forums connected to the known members of Thug Shaker Central, including Mr. Teixeira.

To be sure, the Federal Bureau of Investigation found him first. But investigators must go through legal hurdles, like obtaining court approval for a search warrant. The Times had a chance to knock on Airman Teixeira’s door a few hours before F.B.I. agents arrived to search his home.

Airman Teixeira’s case bears some resemblance to other relatively recent leak cases in which people connected to the military or a spy agency used their access to acquire sensitive documents and posted them online or gave them to the news media.

But Chelsea Manning, who gave documents to WikiLeaks, and Reality Winner and Edward Snowden, who provided documents to the news media and other organizations, were trying to bring attention to things they thought the public needed to know. Airman Teixeira, however, is accused of sharing documents with a small group of acquaintances, rather than trying to reveal them to the wider public.

Justice Department officials have been considering whether to ask the court to move the case to the Eastern District of Virginia, a court where both prosecutors and public defenders have extensive experience handling cases involving classified secrets. While Airman Teixeira is accused of taking the documents from a military base in Massachusetts, much of that material was originally created by the Pentagon, which is in the Eastern District.

That issue is still under consideration, even though prosecutors with the U.S. attorney’s office in Massachusetts favor trying Mr. Teixeira in Boston, according to people familiar with the situation.

Maya Shwayder contributed reporting.