EXCLUSIVE: The House Intelligence and Armed Services Committees are investigating the massive leak of classified national security and defense secrets and documents on the internet, demanding answers from the Pentagon on how such an extensive unauthorized disclosure was able to occur.
House Intelligence Committee Chairman Mike Turner and House Armed Services Committee Chairman Mike Rogers penned a letter to Defense Secretary Lloyd Austin Tuesday, exclusively obtained by Fox News Digital.
The letter comes days after the FBI arrested Massachusetts Air National Guardsman Jack Douglas Teixeira in connection with a trove of classified documents that were leaked online in recent months.
Teixeira, 21, was charged last week with unauthorized retention and transmission of national defense information and willful retention of classified documents.
"The world has watched as classified national security secrets leaked widely and precipitously across the internet," Turner and Rogers wrote. "The unauthorized disclosures appear extensive. The period over which they occurred unnoticed by government authorities is lengthy."
The leaked documents mainly concern Russia's invasion of Ukraine but also include intelligence on China, the Middle East, Israel's spy agency Mossad and world leaders. The Department of Defense has said the documents include "sensitive and highly-classified material."
U.S. defense officials previously told Fox News the leak could be "bigger than Snowden" in terms of damage to intelligence and allied relationships.
"Americans and our allies are asking how such a serious leak was able to occur with such ease and breadth," they added, acknowledging that there is currently an ongoing law enforcement information into the matter.
Attorney General Merrick Garland, last week, used the 1917 Espionage Act when discussing charges against Teixeira, which would carry a sentence of up to 15 years in prison - ten years for the first charge, and five for the second.
And Defense Secretary Lloyd Austin also ordered a review of "intelligence access, accountability and control procedures" to ensure that leaks like this don't happen again.
But Turner and Rogers stressed that it is "imperative" that their committees, which are responsible for oversight, get "immediate access to all relevant and pertinent information necessary to inform the Committees’ determination of whether this incident might be corrected or prevented in the future through legislation or other policy-related adjustments."
"We must ensure national security is not further endangered or harmed by similar crimes happening in the future," they wrote.
By May 1, Turner and Rogers are demanding Austin assist the committees in investigating the "serious breach" by turning over all documents and records associated with the authority to access classified information, and the level and extent of access by Teixeira, along with any documents reflecting "procedures and protections in place at the suspect’s employment base," which was Otis National Guard Base in Massachusetts, for protecting classified information.
Turner and Rogers are also demanding all records associated with the Department of Defense’s review of security procedures at Otis National Guard Base and others, and any Pentagon analysis concerning the "extent and scope" of the classified leak, and whether here are any other documents that "may still be at risk of disclosure."
The lawmakers are also asking for any assessment of other individuals who may have had knowledge or assisted in the unauthorized disclosure, and the universe of all classified documents that are related to the matter.
They also asked for any "written assessment" by the Pentagon concerning "operational ramifications of the current classified leaks."
Turner and Rogers explained that the House Armed Services Committee maintains oversight jurisdiction over the Department of Defense generally, and that the House Intelligence Committee has oversight and legislative jurisdiction of the intelligence, and intelligence-related activities of the Department of Defense.
The Pentagon did not immediately respond to Fox News’ request for comment on the congressional investigation, but a Pentagon spokesperson previously called the leaks a "deliberate criminal act."
Meanwhile, Teixeira, who joined the Air National Guard in September 2019, held the highest level security clearance granted by the federal government for top secret information, according to an internal Department of Defense email reviewed by Fox News.
His security clearance and access to classified government systems have since been revoked, according to another internal government document.
The FBI began surveilling Teixeira in connection with the leaks before Thursday but were forced to accelerate their plans to arrest him after The New York Times identified him last Thursday morning, a source briefed on the investigation told Fox News.
The New York Times report named Teixeira as the leader of a Discord group called "Thug Shaker Central" that consisted of roughly 20 to 30 young men.
Teixeira allegedly starting sharing classified documents with the private group in recent months, but the leaks gained wider attention after another member shared them in a public forum, according to the report.
Investigators don't believe the case ends with Teixeira and are looking at others who may be involved, a source told Fox News.
The National Guard said in a statement it is aware of the "alleged role a Massachusetts Air National Guardsman may have played in the recent leak of highly-classified documents" from the Pentagon.
"The National Guard takes this issue very seriously and will support investigators," the National Guard said in a statement. "National security is our foremost priority, and any attempt to undermine it compromises our values and degrades trust among our members, the public, allies and partners."