The company reported a radiation level of 100 millisieverts per hour at the same tank on 22 August 2013.
The workers at the Japanese nuclear nuclear power plant were allowed to an annual accumulative radiation exposure of 50 millisieverts.
According to TEPCO spokesman, from the latest reading of radiation was partly because investigators had utilized a measuring instrument capable of registering higher amounts of radiation.
Previously, the instruments used had a capacity to measure radiation up to 100 millisieverts, but the latest instruments were able to measure up to 10,000 millisieverts.
Radiation of 220 millisieverts was tracked near an adjacent storage tank, where a reading of 70 had been registered in August 2013.
The company has also found another leak from a pipe that links two tanks near the detected spike.
Radiation of 230 millisieverts was detected from the new leak nearby tanks, a new measurement of 70 was taken from another, separate storage tank.
TEPCO spokesman said, "We have not confirmed fresh leakage from the tank and water levels inside the tank has not changed. We are investigating the cause."
In August 2013, TEPCO reported a leakage of 300 metric tons of contaminated water with high levels of radiation at the Fukushima Daiichi nuclear power plant.
The Nuclear Regulation Authority has raised the severity level from Level 1 ‘anomaly’ to a Level 3 ‘serious incident’ on an International Nuclear and Radiological Event Scale.