John Sopko’s team of investigators has uncovered all kinds of wasteful spending in Afghanistan through its work as a U.S. government watchdog. Now the group has uncovered a $43 million gas station, which Sopko calls “gratuitous and extreme”—and possibly criminal.

In a scathing report, Sopko, the Special Inspector General for Afghanistan Reconstruction, wrote that a similar compressed natural gas station in Pakistan cost $500,000, or about $306,000 at current exchange rates, meaning the Afghanistan station cost 140 times as much.

He wrote that the Pentagon’s program had “several troubling aspects,” including $30 million in overhead costs, and the lack of a feasibility study before the project began.

Sopko said that that the Pentagon essentially shut down when pressed about the program, saying: “One of the most troubling aspects of this project is that the Department of Defense claims that it is unable to provide and explanation for the high cost of the project or to answer any other questions concerning its planning, implementation or outcome.”

The department that was in charge of it, the Task Force for Stability and Business Operations, has closed and so the Pentagon said it couldn’t comment on its activities, Sopko’s letter said.

He wrote that he found 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.”

A Pentagon spokesman did not immediately respond to a request for comment.

Despite the lack of cooperation, Sopko said he intended to continue to investigate the program to see “whether any conduct by TFBSO staff or contractors was criminal in nature.”

The gas station was intended to help Afghanistan curb its dependence on foreign petroleum products and take advantage of domestic energy. But investigators found that Afghanistan does not have the natural gas transmission infrastructure to support a “viable market” for cars that used compressed natural gas.

And the cost of converting gasoline-powered cars to run on natural gas “may be prohibitive for the average Afghan.” The cost to do so is estimated at about $700 per car, while the average annual income in Afghanistan is $690.

“In sum, Sopko wrote, “it is not clear why [TFBSO] believed the CNG filling station should be undertaken.”

The project also angered Sen. Claire McCaskill (D-Mo.), a member of the Armed Services Committee, who wrote a letter to Defense Secretary Ashton Carter demanding answers about the station.

“There are few things in this job that literally make my jaw drop,” she said in a statement. “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.”

Sen. Chuck Grassley (R-Iowa) took aim at the Pentagon saying, “The lack of accountability and transparency is disgraceful. The Defense Department needs to come clean, drop the obfuscation, and hold people responsible for a colossal waste of tax dollars.”