Three Japanese naval officers who swapped pornography on their computers triggered a scandal over a possible leak of sensitive data linked to Japan's missile defense system, a newspaper said on Thursday.
Police launched a probe last week after a navy officer married to a Chinese woman was found to have taken home a computer disk containing information about the high-tech Aegis radar system, domestic media said.
Aegis is used on Japanese destroyers that are to be fitted with SM-3 missile interceptors from this year as part of the missile defense program.
The officer told police he accidentally copied the confidential data onto his computer's hard disk when copying porn from a computer belonging to a crew member from another destroyer, the Yomiuri newspaper reported.
A third officer was also found to have copied data on the Aegis system alongside pornographic images, the Yomiuri said.
Police suspect senior officers were also involved in the swap because none of the three were authorized to access the confidential information, the Yomiuri said.
Japan sped up the implementation of its missile defense program after North Korea fired a volley of ballistic missiles last year. Last Friday, its first ground-based interceptors were trucked into Iruma air base in Saitama prefecture, north of Tokyo, to protect the capital.
Any defense leak could potentially affect Japan's biggest ally, the United States, whose navy also uses the Aegis system.
"I'm aware of the ongoing investigation," Bruce Wright, the commander of U.S. forces in Japan, told reporters.
"We take operational security very seriously in the U.S. military. I know the Japan Self-Defense Forces also take operation security seriously."
Spokesmen for the Defence Ministry and local police declined to comment on the investigation.