It might be the world's most expensive gas station — not to mention a gross misuse of taxpayer money, according to a top government watchdog. 

The Department of Defense spent $43 million to build a gas station in Afghanistan that should have cost roughly $500,000, the lead oversight team monitoring U.S. spending in Afghanistan has found. The discovery came as part of a broader investigation into allegations of criminal activity within the DOD's premiere program to kick-start the Afghan economy. 

"It's fright-night at the Pentagon," John Sopko, special inspector general for Afghanistan reconstruction (SIGAR), told, calling the spending "outrageous to the taxpayer."

At issue is spending by the Task Force for Stability and Business Operations, known as TFBSO or the Task Force, which ended in March 2015. But most alarming, according to Sopko, is the DOD's failure to answer questions about the $800 million program and its claim the Task Force's employees no longer work for the DOD.

"I have never in my lifetime seen the Department of Defense or any government agency clam up and claim they don't know anything about a program," said Sopko, a former federal prosecutor appointed by President Obama in 2012 to watch over spending in Afghanistan.

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"Who's in charge? Why won't they talk?" he said. "We have received more allegations about this program than we have received about any other program in Afghanistan."

In a report released Monday, SIGAR detailed how TFBSO's Downstream Gas Utilization Project set out to build a compressed natural gas (CNG) filling station in the Afghan city of Sheberghan in 2011. The U.S. Geological Survey found in 2006 that northern Afghanistan is rich in natural gas reserves, and the Task Force sought to make the compressed natural gas commercially viable by constructing the facility -- and more broadly, helping to reduce the war-torn country's dependence on costly imported gas.

The Task Force struck a contract with Central Asian Engineering, which received just under $3 million from the U.S. government to construct the Sheberghan gas station. Sopko noted the cost of building a similar gas station in neighboring Pakistan is no more than $500,000.

But the final tab in Sheberghan would turn out to be astronomically higher.

The Task Force spent $42,718,739 between 2011 and 2014 to "fund the construction and to supervise the initial operation of the CNG station," the U.S. military told SIGAR -- with "approximately $12.3 million in direct costs and $30 million in overhead costs."

Who approved all that funding and why are questions the DOD will not answer, according to Sopko.

In an Oct. 22 letter to Defense Secretary Ashton Carter, Sopko asked why no one at the DOD could speak about the nearly-billion dollar TFBSO program, which had reported directly to Carter.

"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. "Nevertheless, I intend to continue our inquiry."

Sopko was responding in part to a June 17 letter from Brian McKeon, the principal deputy under secretary of defense for policy. McKeon had told Sopko in response to earlier questions that "the closure of TFBSO in March 2015 and departure of all its employees have resulted in the Office of the Secretary of Defense (OSD) no longer possessing the personnel expertise to address these questions or to assess properly the TFBSO information and documentation retained by WHS in the OSD Executive Archive."

"It is totally incredible that you now have a ghost program in the Department of Defense," Sopko told "It’s almost like it's pixie dust."

SIGAR said it is unable to determine whether the CNG station in Sheberghan is currently operational. But government documents obtained by the oversight team show that Qashqari Oil and Gas Services -- the business that took over the station in 2014 -- did not renew its business license six months later, in November 2014.

The TFBSO was originally created by the DOD to revitalize Iraq's economy after the U.S.-led invasion in 2003. The program was redirected to Afghanistan in 2009 to lead projects supporting economic development.

Sopko said his office has received "numerous allegations" of criminal activity by the Task Force from former employees as well as "current and former uniformed officers who worked over there, other agencies and contractors." He declined to elaborate on the specifics of the accusations.

A review by shows at least one employee -- Joseph Catalino, the former head of the Task Force -- is still employed by the Defense Department in a senior role.

According to a congressional source, Catalino was in charge of TFBSO in Afghanistan before beginning work in June as a senior adviser in the Office of the Assistant Secretary of Defense for Special Operations and Low Intensity Conflict. The DOD's personnel office confirmed Catalino's employment and current job title.

A senior defense official, speaking on background, said Sopko and his team have access to extensive records archived with Washington Headquarters Services (WHS), and he disputed any suggestion of a deliberate effort by the DOD to conceal information.

The official, however, told he could not name any current DOD employees with detailed knowledge of the gas station project and said decisions made on its construction predated Catalino’s time as head of the Task Force. The official said he did not know whether the gas station was currently functional.

Sopko said billions of U.S. dollars have been wasted to date in Afghanistan. In its quarterly report to Congress, released Friday, SIGAR said the U.S. has provided $8.4 billion for counter-narcotics efforts in Afghanistan since 2002, yet the country remains the world's leading producer of opium.

SIGAR's report on the $43 million gas station spurred outrage among U.S. lawmakers in both parties who called for a thorough investigation into the program's finances.

"There's few things in this job that literally make my jaw drop," Sen. Claire McCaskill, D-Mo., said in a statement to "But of all the examples of wasteful projects in Iraq and Afghanistan that the Pentagon began prior to our wartime contracting reforms, this genuinely shocked me."

"It’s hard to imagine a more outrageous waste of money than building an alternative fuel station in a war-torn country that costs more than 8,000 percent more than it should, and is too dangerous for a watchdog to verify whether it is even operational," said McCaskill, who penned a letter to Carter on Monday demanding information. "Perhaps equally outrageous however, is that the 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."

Sen. Chuck Grassley, R-Iowa, echoed McCaskill's call for transparency and said, "Under the law, government employees are not authorized to spend tax dollars without proper documentation like contracts, invoices, receiving reports and payment vouchers." 

"If those documents don't exist, that's a huge problem," Grassley said. "The Defense Department needs to come clean, drop the obfuscation, and hold people responsible for a colossal waste of tax dollars."

Cristina Corbin is a reporter for Follow her on Twitter @CristinaCorbin