Originally Published: 02 AUG 22 15:30 ET

Updated: 02 AUG 22 19:24 ET

By Tierney Sneed and Zachary Cohen, CNN

(CNN) -- The Defense Department wiped the phones of top departing DOD and Army officials at the end of the Trump administration, deleting any texts from key witnesses to events surrounding the January 6, 2021, attack on the US Capitol, according to court filings.

The acknowledgment that the phones from the Pentagon officials had been wiped was first revealed in a Freedom of Information Act lawsuit American Oversight brought against the Defense Department and the Army. The watchdog group is seeking January 6 records from former acting Secretary of Defense Chris Miller, former chief of staff Kash Patel, and former Secretary of the Army Ryan McCarthy, among other prominent Pentagon officials -- having filed initial FOIA requests just a few days after the Capitol attack.

Miller, Patel and McCarthy have all been viewed as crucial witnesses for understanding government's response to the January 6 Capitol assault and former President Donald Trump's reaction to the breach. All three were involved in the Defense Department's response to sending National Guard troops to the US Capitol as the riot was unfolding. There is no suggestion that the officials themselves erased the records.

The government's assertion in the filings that the officials' text messages from that day were not preserved is the latest blow to the efforts to bring transparency to the events of January 6. It comes as the Department of Homeland Security is also under fire for the apparent loss of messages from the Secret Service that day.

Miller declined to comment. Patel and McCarthy did not immediately respond to requests for comment. The US Army Public Affairs media relations chief, Col. Cathy Wilkinson, said in a statement that, "It is our policy not to comment on ongoing litigation."

Paul Ney, former general counsel for the Department of Defense, told CNN that Tuesday's revelation is the "first I've heard about DoD litigation in which there is any issue with the cell phone I turned in when I left DoD on January 20, 2021.

"I did not wipe the phone before I turned it in (or ever that I can recall)," Ney continued. "When I turned the phone in, I did not know what was going to be done with that device nor do I know what actually was done with that device after I turned it in. If DoD represented in litigation that the device was wiped after I left DoD on Inauguration Day, I believe that is very likely what happened and when it happened, but I do not know why."

American Oversight is now calling for a "cross-agency investigation" by the Justice Department to investigate destruction of the materials.

"It's just astounding to believe that the agency did not understand the importance of preserving its records -- particularly [with regards] to the top officials that might have captured: what they were doing, when they were doing it, why they were doing, it on that day," Heather Sawyer, American Oversight's executive director, told CNN.

Sawyer said that her organization learned the records were not preserved from government attorneys earlier this year, and that acknowledgment was then memorialized in a joint status report filed with the court in March.

"DOD and Army conveyed to Plaintiff that when an employee separates from DOD or Army he or she turns in the government-issued phone, and the phone is wiped," the government said in the filing. "For those custodians no longer with the agency, the text messages were not preserved and therefore could not be searched, although it is possible that particular text messages could have been saved into other records systems such as email."

The acknowledgment that the records were not preserved has taken on new significance in the wake of the ongoing scandal over the loss of Secret Service agents' texts from January 6.

"It just reveals a widespread lack of taking seriously the obligation to preserve records, to ensure accountability, to ensure accountability to their partners in the legislative branch and to the American people," Sawyer said.

The Secret Service has said that its texts were lost as a result of a previously scheduled data migration of its agents' cell phones that began on January 27, 2021, exactly three weeks after the attack on the US Capitol. Homeland Security Inspector General Joseph Cuffari first learned those texts were missing as early as May 2021, CNN previously reported.

The pattern across multiple agencies has prompted her organization to write to Attorney General Merrick Garland, who is already facing a request from congressional Democrats that he take over the DHS' probe into the missing Secret Service texts.

"American Oversight accordingly urges you to investigate DOD's actions in allowing the destruction of records potentially relevant to this significant matter of national attention and historical importance," the letter said, while citing calls from Democratic Sen. Dick Durbin that the Department of Homeland Security be investigated for similar failures, the letter, shared with CNN on Tuesday, said.

After filing the FOIA requests with the Defense Department and the Army, American Oversight says the Pentagon acknowledged the request on January 15, 2021. American Oversight then filed a lawsuit that March to force disclosure of the records. In addition to the FOIA obligations American Oversight says the Pentagon has ignored in failing to preserve the records, Sawyer also pointed to a separate federal records law also require that the government preserve records that have "informational value of the data in them."

"I think it's highly unlikely that anyone could argue with a straight face that communications happening between these top officials on January 6 would not have the type of informational value that the Federal Records Law is meant to reach," Sawyer said. American Oversight is seeking records for several other Pentagon officials -- some of whom remain within government service.

"For those custodians still with the agency, Army has initiated a search for text messages responsive to the FOIA requests, and estimates completing their supplemental search by the end of September," the Justice Department said in the July joint filing said in the case.

A spokesperson for the Justice Department declined to comment.

What the Pentagon was hearing from the White House as the Capitol attack unfolded has been a focus of the House January 6 investigation, and lawmakers say that addressing the security lapses of that day is an aim of their probe.

The House January 6 committee last week released testimony Miller gave to the panel denying that former President Donald Trump ever game him a formal order to have 10,000 troops ready to be deployed to the Capitol on January 6.

"I was never given any direction or order or knew of any plans of that nature," Miller said in the video.

A spokesman for the January 6 committee declined to comment on records related to the Pentagon.

A former Defense Department official from a previous administration told CNN that it is ingrained into new hires during their onboarding that their work devices were subject to the Presidential Records Act and indicated their communications would be archived. The source said it was assumed when they turned in their devices at the end of their employment, any communication records would be archived.

This story has been updated with additional details.