Japan's Nuclear Regulation Authority has issued a warning to the operator of the crippled Fukushima Daiichi nuclear power plant for not complying with rules to safeguard nuclear materials. The regulator says the company was not keeping a list of keys to the reactor buildings.
Tokyo Electric Power Company is working to decommission the plant. The company told the regulator last December that a key to one of the buildings was missing.
An investigation revealed that workers did not notice the key was missing for more than a week because there was no list of keys.
NRA officials found more than 9,000 keys to open another padlock on a door of the reactor No.1 building.
TEPCO officials say that they are investigating why there are so many keys.
The missing key is thought to have been incinerated with trash. Most of the padlock keys have been kept in a location separate from the reactor building and apparently have not been in use.
They say the lock to the door has been replaced and there is now a list of registered keys.
The officials say they will abide strictly by the rules to protect nuclear materials.