The season's 19th typhoon, Hagibis, slammed into Japan over the weekend causing dozens of casualties and leaving many regions flooded.
Hagibis also swept across Fukushima, home to the nuclear plant that melted down following the 2011 earthquake and tsunami.
According to Japanese media, the city of Tamura in Fukushima Prefecture said Sunday that an unknown number of bags containing contaminated waste from the plant were lost.
Officials say heavy rains carried the bags to the nearby Furumichi River.
That river connects to another river and flows into the Pacific Ocean.
The city retrieved ten bags from the river but they haven't been able to confirm how many went missing out of the more than 2-thousand 6-hundred bags kept in a temporary storage.
Each bag weighs between 700 kilograms and one.three tons.
They contain grass and wood collected from areas that were heavily contaminated by radiation.
City officials insist contaminated waste did not leak out of the bags and they will carefully check the storage and management records.
However, this isn't the first time something like this has happened.
In 2015, contaminated waste from the Fukushima plant went missing in similar circumstances when the region was hit by torrential downpours.
Lee Min-sun, Arirang News.