An apparent miscalculation amid a typhoon caused a storage tank to overflow at the wrecked Fukushima No. 1 power plant, releasing about 430 liters of radioactive water into the Pacific Ocean, Tokyo Electric Power Co. said Thursday.

Authorities are still groping for a solution to the water crisis at the crippled nuclear plant, which is rapidly running out of storage space and facing a growing risk of flooding from typhoons.

Around 8 p.m. Wednesday, plant workers checking a group of five flange-type tanks in a storage sector called B-South discovered water leaking from the cover of a tank that had apparently been overfilled. Because the group of interconnected tanks was built on a slope, the water was coming out of the one farthest downhill — and landing outside the flood containment barrier encircling it.