Workers at the crippled Fukushima Daiichi nuclear plant have found a leak of highly radioactive water from a waste water tank.

Its operator, Tokyo Electric Power Company, says the water likely leaked from a seam of the tank.

The leaked water was spotted on Wednesday on the side of one of an array of steel tanks holding contaminated water that is continuously generated at the site.

TEPCO’s analysis found 590,000 becquerel per liter of beta-emitting radioactive materials in the water.

Tokyo Electric estimates that 32 liters of such highly radioactive water had trickled out, mixed with rainwater, and remained within a barrier around the tank.

Workers moved water in the tank to another one to lower the water level enough to halt the leak.

The leaking cylindrical tank is made by splicing steel plates with bolts. But they have had waste water leaks in the past from seams.

The operator has been replacing these leak-prone tanks with new seamless ones. But the increasing volume of waste water makes it difficult for the utility to completely do away with the old ones.