The U.S. Department of Defense spent nearly $43 million on a gas station in northern Afghanistan and has been unable to explain why it cost so much, a U.S. special inspector reported on Monday.

The Pentagon ‚"charged the American taxpayers $43 million for what is likely to be the world's most expensive gas station," said John Sopko, head of the Special Inspector General for Afghanistan Reconstruction, a congressionally mandated body. The amount was spent between 2011 and 2014 on construction and initial implementation of the station.

The gas station in Sheberghan, Afghanistan opened in 2012 and was created to show that compressed natural gas could be used in Afghanistan in cars effectively.  

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However, the task force behind the project closed operations in March and for that reason, according to the report, the Department of Defense said it did not possess ‚"the personnel expertise to address these questions."

"Frankly, I find it both shocking and incredible that (the Defense Department) asserts that it no longer has any knowledge," the report said. It added that the task force reported directly to the Office of the Secretary of Defense and was an $800 million program.

The report found that a compressed natural gas filling station in neighboring Pakistan costs no more than $500,000 to construct. That would make the gas station in Afghanistan more than 140 times more expensive.

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A Defense Department spokesman said the Pentagon continues to provide access to documents to SIGAR through a reading room.

"Further, we have offered to assist SIGAR in locating and contacting any former TFBSO (Task Force for Business and Stability Operations) personnel they wish to interview," said Army Lieutenant Colonel Joe Sowers.

Nearly $110 billion have been appropriated in Washington for reconstruction in Afghanistan since 2002, when U.S. forces drove the Taliban from power for harboring militants from al Qaeda, which carried out the Sept. 11, 2001, attacks.