With the United States, Germany and other Western countries trying to tighten sanctions on Iran to slow its nuclear program, the MCS mystery demonstrates the difficulty of tracking the flow of technology and material that have civilian and military applications.

“Where we have dual-use technology, it is not easy to control simply by checking goods,” said Wolfgang Schmitz, a spokesman for the German Customs Investigations Bureau. “You need more info about the contract and the possible criminal elements inside it.”

One of the dual-use materials at MCS was carbon fiber, which is often used in the aerospace and automotive fields because of its extreme strength, resistance to heat and light weight. MCS used carbon fiber to build high-
pressure gas tanks for compressed natural gas and hydraulic systems. More than 2,600 pounds of the material still sits inside the plant.

Carbon fiber’s strength and heat resistance also make the material essential for advanced centrifuges. The cylindrical machines spin at supersonic speeds to enrich uranium, which can be used to fuel civilian nuclear plants or, at higher concentrations, to make fissile material for atomic weapons.