Police arrested three individuals, including the head of a trading company, on Tuesday, on suspicion that they unlawfully exported to a Chinese firm a carbon fiber material that can be diverted to military use.
The China-based importer is linked to Chinese and other foreign military enterprises, the police said, raising the possibility that the material could have wound up in an end-user country such as Iran.
Those arrested were identified as Shoji Kondo, 75, chairman of a Hyogo-based trading company, Norio Miyake, 57, the company's sales manager, and Shin Tanesa, 66, a sales agent.
It is the first time anyone in Japan has been arrested over illegal exports of carbon fiber, the police said.
Investigators suspect the three exported without government permission some 3,500 kg of carbon fiber made by Toho Tenax Co. to China via Busan, South Korea, in January 2010, by falsely declaring the end user was a South Korean firm.
The three denied the allegations. They said it was their understanding the carbon fiber would go no farther than South Korea, according to the police.
Carbon fiber exports are strictly controlled as the flexible fiber that is 10 times stronger and four times lighter than iron can be used in making centrifuges for the enrichment of uranium as well as in building military aircraft.
While it is also used in sports equipment, civilian aerospace and the auto sector, the export of high-specification material requires government permission.