Tokyo Electric Power Co. said Sunday it has postponed the transfer of radioactive water from a leaking underground tank at the crippled Fukushima Daiichi nuclear power plant because it needs more time to conduct safety checks and install a water pipe.

The operator of the crisis-hit plant in northeastern Japan had planned to start moving contaminated water from the No. 2 tank to an above-ground container located about 400 meters away.

However, the utility known as Tepco discovered Thursday that about 22 liters of contaminated water had leaked from a junction of the piping for transferring liquid from the No. 3 tank to the No. 6 tank.

Since the radioactive water from the No. 2 tank was also to go through the junction, company officials now say it will take several more days to put in place a new pipe to be used to transfer the water and inspect it.

From the No. 2 tank, up to 120 tons of contaminated water may have leaked into the soil. Smaller amounts of radioactive water have also leaked from the No. 1 and No. 3 tanks.

Tepco has decided to pump out a total of 23,600 tons of liquid to tanks above ground by the end of June. The leaking underground containers have been used to store water for cooling reactors which experienced meltdowns during the 2011 nuclear crisis at the plant.