The operator of a nuclear facility, north of Tokyo, says radioactive substances leaked while workers were changing plastic bags and packing a container with material for nuclear fuel inside.
The Japan Atomic Energy Agency made the revelation on Thursday, a day after it reported a detector of radioactive substances sounded the alarm at its Nuclear Fuel Cycle Engineering Laboratories in Tokai Village, Ibaraki Prefecture. The facility was previously used to produce nuclear fuel.
The agency said nine workers were present at the site, and none of them suffered radiation exposure.
At a news conference on Thursday, agency officials said that they have found radioactive substances leaked in one of the rooms.
The officials say four of the nine workers in the room took the container out of an airtight box called a "glove box" and wrapped it with two plastic bags.
They say the alarm went off immediately after the workers checked for contamination and they detected radioactive material.
The operator suspects that the sealing of the first plastic bag may have been insufficient or there may have been a hole in the bag.