Updated

The operator of Japan's tsunami-damaged nuclear plant says a power failure has left three fuel storage pools without fresh cooling water for hours.

Tokyo Electric Power Co. says the blackout Monday night at the Fukushima Dai-ichi plant was brief at its command center but continued for hours at three of the seven fuel storage pools and a few other facilities.

TEPCO says the reactors were unaffected, and it plans to restore power to the pool cooling systems as soon as it determines the cause. It says the nuclear fuel stored in the pools will remain safe for at least four days without fresh cooling water.

The March 11, 2011, earthquake and tsunami destroyed the plant's power and cooling systems, causing three reactor cores to melt and fuel storage pools to overheat. The plant is now using makeshift systems.