North Korea’s state-run media say traces of radioactive materials have been detected in the North.

The deputy head of a state-run weather research center, Sim Myeong-ok, appeared on Korean Central Television on Tuesday evening and said that traces of radioactive iodine and cesium were found in radiation observatories in Pyongyang, Wonsan and Cheongjin. Sim said that such substances had not been detected before.

Without elaborating on the exact amount of the substances that were detected, he only said that the amount of such substances is miniscule and would have very little effect on the human body.

The official said radioactive materials could have entered the North via easterly winds, which he said was constantly blowing during the spring and summer.

During its weather forecast, the Korean Central Television said that the North will see heavy precipitation on Wednesday and urged people to avoid getting wet from the rain, saying that the rainwater could contain radioactive substances originating from Japan.