The $43 million CNG station constructed in Afghanistan by the Task Force for Stability and Business Operations. Central Asia Development Group / SIGAR

The Department of Defense did not immediately respond to a request for comment from Al Jazeera.

SIGAR’s report was based on a study by the Task Force for Business and Stability Operations (TFBSO), established by the Department of Defense in 2006 to bolster the economies of post-U.S.-occupation Iraq and Afghanistan.

The TFBSO study showed that the Department of Defense spent $42,718,739 from 2011 to 2014 to build the gas station and that its goal was to further Afghanistan’s reliance on its own natural resources.

From 1980 to 2012, Afghanistan imported 100 percent of its refined petroleum products, the report said, adding that CNG “costs approximately 50 percent less than a comparable amount of gasoline in Afghanistan and burns cleaner than gasoline.”

The SIGAR report blasted the Department of Defense for failing to provide an explanation for the overspending.

“One of the most troubling aspects of this project is that the Department of Defense claims that it is unable to provide an explanation for the high cost the project or to answer any other questions concerning its planning, implementation or outcome,” the special inspector general for Afghanistan reconstruction, John F. Sopko, said in a letter to Defense Secretary Ashton Carter that accompanied the report.

Sopko told Al Jazeera in June that the United States has been wasteful in Afghanistan. He said Washington built “things that didn’t work; things that the Afghans didn’t know about, didn’t want or can’t use; and things that can’t be sustained.”

“We identified, for example, $400 [million] to $500 million for airplanes that the U.S. purchased for the Afghan air force. The Afghan air force couldn’t use them. They were the wrong planes for the country. They basically had to be destroyed, and we got three cents on the dollar,” he said.

SIGAR in December 2014 published a report saying that U.S. development authorities failed to track the results of millions of dollars spent to improve medical care and professional training for women in Afghanistan.