The Japanese Ministry of Defense deployed T4 training aircraft for possible radioactive particles after the nuclear test conducted by North Korea, the government said.
"To understand the impact of potential radioactive waste after the nuclear test, the apparatus of air self-defense forces have collected dust" in the air, said a government spokesman Yoshihide Suga.
"The samples are on their way to the center of chemical analysis of Japan," he added.
Suga said the aircraft remained in Japanese airspace. According to the newspaper Sankei Shimbun, the apparatus took off three bases in several regions.
Checkpoints distributed in Japan detected no abnormal radiation level so far, the spokesman added.