Japan's crippled Fukushima nuclear power plant is at it again, this time leaking 114 gallons of highly radioactive contaminated water into the Pacific Ocean.

The leak, according to Tokyo Electric Power Co. (TEPCO) on Thursday, came from a storage tank overfilled with contaminated rainwater.

The company said the leak happened where the side connects with the top part of the tank with the bolts. It occurred due to workers' miscalculations as to how much amount of water the tank could be containing, the company said, noting that the tank was sitting on a slope.

A TEPCO spokesman told a press conference in Tokyo on Thursday that the leak happened because workers miscalculated the amount of water the tank was capable of holding due to it sitting on a slope.

"We believe [contaminated water] flowed into the ocean," Masayuki Ono, acting general manager of Tepco's Nuclear Power and Plant Siting Division, said.

Video Source: Youtube/NTDTV

TEPCO said the spilled water had radiation readings 6,700 times higher or as high as 200,000 becquerels per liter. The legal limit is 30 becquerels per liter.

Just on Tuesday this week, TEPCO had revealed that an operation to transfer water between holding tanks had leaked four tonnes of contaminated rainwater. The company assured however that these held low levels of radiation.

A magnitude 9 earthquake hit Japan in March 2011. The resulting and tsunami severely crippled the Fukushima Daiichi nuclear power plant facility. Three of its units suffered nuclear meltdowns and hydrogen explosions.

TEPCO had chosen to remain mum on the possible radiation leakage since being hit by the tsunami. But in August, TEPCO and Japan admitted Fukushima had leaked about 300 tonnes of radioactive water from another holding tank into Pacific Ocean.