Tokyo Electric Power Co. says it has found that an unspecified amount of water contaminated with a highly concentrated radioactive substance escaped from another storage tank at the Fukushima No. 1 nuclear plant and some may have reached the Pacific Ocean.

Tepco said Wednesday it detected 200,000 becquerels per liter of beta ray-emitting radioactive substances, including strontium-90, far above the legal limit of 30 becquerels per liter, as well as cesium-134 and -137, both within their legal limits.

A ditch adjacent to the tank is linked to a drainage channel reaching the ocean. "Contaminated water may well have flowed into the sea," Tepco said.