The Pentagon has withheld key documents relating to abuses at Afghanistan’s Dawood Military Hospital, a former top military doctor in Afghanistan told BuzzFeed.

Internal Department of Defense rulings about what material to hand over to Congressional investigators "excluded the vast majority of documents from the get-go that would have related to the Dawood Khan Hospital," Colonel Schulyer Geller said in an interview on Monday.

Geller, who served as Command Surgeon of the NATO Training Mission in Afghanistan, and two other military officials testified last week in front of the House Oversight and Government Reform Committee, detailing horrific abuse and neglect at a U.S. funded hospital in Kabul, as well as Gen. William Caldwell's role in covering up evidence of the hospital's condition.

The failure to release the documents follows a pattern of what Congressional investigators described as the Pentagon's aim to "obstruct" the committee's efforts in getting at the truth.

"Individuals within the Department may have withheld [documents] in an effort to obstruct the Committee's oversight," wrote Rep. Jason Chaffetz to Secretary of Defense Leon Pannetta on July 15.

The Pentagon refused to release the majority of evidence from the field on a technicality, claiming Congress had no oversight over a NATO command, according to Geller.

The DoD ruled that documents marked with NATO or ISAF (International Security Assistance Force) were ineligible for release to the Congressional committee, he said.

Geller called this decision “very unusual” given the United States’ position in NATO, saying that only ISAF documents approved by NATO headquarters could be released.

Pentagon spokesperson Commander William Speaks denied the claim, and emailed that the DoD release did "include NATO/ISAF information," noting that a total of 2,074 pages of records had been provided to the committee.

The House Oversight and Government Reform Committee did not comment on the DOD’s failure to release the majority of NATO documents.

The DoD does not usually distinguish between ISAF and U.S. documents in this manner, according to Geller.

“With that ruling, they could withhold the majority of the information that had been generated by the mentors over 2010 – 2011,” Geller said. There were some two dozen mentors — U.S. military personnel tasked to train Afghan forces — overseeing the wards at the Dawood Hospita at any one time. The U.S. advisors had the most direct and consistent access to patients, and their hospital records with this crucial information carried the NATO seal.

That wasn't the first sign of obstructionism, according to Congressional investigators and whistleblowers.

On Dec. 9, 2011 Geller, who was the command surgeon at the time, submitted a detailed report to the Pentagon.

The report was titled, in part: "Memorandum for Record...Re: Corruption and Mismanagement at the National Military Hospital in Kabul Afghanistan."

Congress wanted the Pentagon to provide them with a copy of this memorandum, as well.

But instead of releasing Geller's memorandum to the committee — which included allegations that Gen. William Caldwell helped block the original hospital investigation — DoD officials sent a watered down timeline to the committee, scrubbing all references to Caldwell.

The committee was incensed, demanding that Panetta "look into whether this document or any other material information may have been intentionally withheld from this committee," according to a letter from Chaffetz.

The DoD Inspector General said it provided all documents necessary, according to Speaks, the Pentagon spokesman.

Military officials speculate that the Pentagon may be fearful of examining Caldwell's role in the scandal too closely, as it could hurt the legacy of the $11.2 billion a year training mission that the U.S. is pinning its withdrawal strategy on.

Caldwell, a West Point graduate, is part of powerful network of military officers within the defense establishment. His chief of staff, for instance, Col. Joseph Buche, was a fellow at the Center for a New American Security, an influential Washington think tank that regularly has both prominent journalists and retired generals on its payroll.

Caldwell's supporters say that he was diligent about investigating the conditions at the hospital.

But three senior military officers testified that, on learning of the abuses at the hospital in August 2010, Caldwell's major concern was that no bad news get out before the 2010 elections.

“The evidence is clear to me that this was politics with a small p - personal career driven politics," wrote Col. Gerald N. Carozza in his testimony to the Oversight Committee, referring to Caldwell's decision to halt the initial investigation.

Caldwell's command also issued orders to destroy any photos or videos from the hospital. "Unofficial personal photos or video or audio recordings of patients or health care events...which already exist will be destroyed or deleted," read a Sept. 12, 2011 memorandum to the Command Surgeon or Medical Training Advisory Group.

Despite Caldwell's alleged attempt to block the investigation, U.S. military personel went ahead and alerted the Inspector General's office to the "Auschwitz-like" conditions at the hospital.

There are currently two ongoing investigations into Gen. Caldwell, though he's yet to testify before the committee.

"I will not speak for Congress, but we are not aware of a request for LTG Caldwell to testify, and have not made anyone unavailable to do so," Commander William Speaks, the Pentagon spokesperson, told BuzzFeed. "DoD is fully cooperating with the ongoing DOD IG review concerning LTG Caldwell."