In 2011, the US built a $43 million natural gas filling station in Afghanistan, which government auditors figure is about $42.5 million more than it should have cost—before you take into account that very few Afghan cars appear to run on compressed natural gas.

But if that is absurd, consider why we still aren’t sure where that money went. The shorthand is that the Department of Defense won’t say or doesn’t know, but that gives short-shrift to the story: We know where the records and people are, but a fight between the DoD and its auditor is keeping them out of the public eye.

The gas station was built by an initiative called the Task Force for Stability and Business Operations (TFBSO), which spent $766 million on Afghan reconstruction between 2010 and 2014. The Special Inspector General for Afghanistan Reconstruction (SIGAR), John Sopko, began looking into TFBSO’s operations in December 2014, after receiving allegations of mismanagement related to the petroleum and mining sectors, but the task force was shuttered in March 2015, its records archived and its staff sent on their merry way.

“Frankly, I find it both shocking and incredible that DOD asserts that it no longer has any knowledge about TFBSO, an $800 million program that reported directly to the Office of the Secretary of Defense and only shut down a little over six months ago,” Sopko wrote in his report (pdf).

When Sopko’s office made specific inquiries about the $43 million gas station, the Pentagon refused to simply send over the relevant documents; instead, SIGAR staff could review them in a supervised Pentagon reading room. The Pentagon had never before required this of Sopko’s team, and justified the change ”as necessary due to SIGAR’s actions that revealed Personally Identifiable Information in an unrelated incident.”

That incident was part of the release of data on $2 billion in discretionary spending in Afghanistan after ProPublica filed a freedom of information act request with SIGAR. The publication did not redact the names of service members who approved spending requests when it published the information. Now, the DOD is apparently retaliating against SIGAR for sharing this information with the public.

“We continue to provide complete and unfettered access to TFBSO documents to SIGAR through the reading room,” Lt. Colonel Joe Sowers told Quartz, who notes that the Government Accountability Office followed similar procedures during a 2011 audit. “Further, we have offered to assist SIGAR in locating and contacting any former TFBSO personnel they wish to interview.”

But, according to SIGAR’s report, multiple staff visits to the reading room ended when archivists “ultimately never produced any documents for SIGAR to review.” As to contacting former personnel, a SIGAR official notes that DOD previously claimed that they didn’t have anyone available who could field questions about the gas station. “Now DOD is saying that it will make someone available, but has yet to provide SIGAR with any names,” the official says.

One possible name on the list is Joseph Catalino, who was the deputy and then acting director of TFBSO from March 2013 through the termination of the program, and is now a senior adviser on special operations at the DOD. Quartz has asked the DOD to speak to Dr. Catalino.

One source close to the IG investigation, but unauthorized to comment on it, said the DOD’s refusal to follow the usual rules “is not unfettered access … if it doesn’t violate the spirit of the Inspector General act, it undermines the spirit.”

With the inspector general in a stand-off with the department under audit over access to documents, and the Defense Department arguing that their auditor can’t be trusted, it looks like it will fall to Congress to uncover the truth. Luckily, members seem interested.

“It’s hard to imagine a more outrageous waste of money than building an alternative fuel station in a war-torn country that costs 8,000 percent more than it should, and is too dangerous for a watchdog to verify whether it is even operational,” Senator Claire McCaskill said in a statement. “[T]he Pentagon has apparently shirked its responsibility to fully account for the taxpayer money that’s been wasted—an unacceptable lack of transparency that I’ll be thoroughly investigating.”