Story highlights TEPCO says it discovered highly contaminated water leaking from a tank

An estimated 100 metric tons flowed over a barrier and onto the ground, it says

The company says it has shut off the flow of water into the tank and the leak has stopped

TEPCO has struggled to manage the vast amounts of tainted water at crippled plant

A large amount of radioactive water has leaked from a holding tank at Japan's troubled Fukushima Daiichi nuclear power plant, its operator said Thursday.

The leak of an estimated 100 metric tons of highly contaminated water was discovered late Wednesday, Tokyo Electric Power Company (TEPCO) said in a statement.

The tainted water flowed over a barrier around the tank and is being absorbed into the ground, TEPCO said. The plant has shut off the inflow of water into the tank and the leaking has stopped, it added.

The company doesn't believe that there was any leakage of the radioactive water into the nearby Pacific Ocean.

Since the massive earthquake and tsunami that hit northeastern Japan in March 2011 set off meltdowns at three of the reactors at the nuclear plant, TEPCO has been storing the enormous volumes of water contaminated at the site in a steadily growing collection of containers.

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The company has struggled to manage the vast amounts of radioactive water, with a number of leaks reported last year.

Prime Minister Shinzo Abe's government vowed to step in to deal with the toxic water crisis at the plant that caused concern in Japan and abroad about the scale of the problem faced by TEPCO.

The leak reported Thursday is one of the largest since TEPCO reported last summer that about 300 tons of radioactive water had leaked from a tank.

CNN first learned about the latest incident on Twitter.