Tokyo Electric Power Company (TEPCO) said Tuesday that it had detected radioactive seawater in the Pacific Ocean with a concentration of radioactive iodine many million times the legal limit.

The operator of the striken Fukushima Daiichi (No.1) nuclear power plant said that samples taken from seawater near one of the reactors contained 7.5 million times the legal limit for radioactive iodine on April 2.

This marks the highest concentration of iodine-131 detected in seawater since the March 11 quake and tsunami damaged Fukushima Daiichi nuclear power plant to the extent it has been freely spewing radioactive material into the sea, land and air.

TEPCO did note however that two days later, the figure dropped from 7.5 to 5 million times above the legal limit for radiation and once again issued their well-rehearsed statement claiming the contamination still does not pose an "immediate danger" and would have "no immediate impact" on the environment.

But while Japan's Nuclear and Industrial Safety Agency said Tuesday that radiation dissipates quickly in the Pacific Ocean, they have also conceded they have no idea what the long-term affects of nuclear contamination will be on marine life.

The delay in the latest figures reaching the public comes as the beleaguered utility firm had to recheck its samples as the firm was lambasted by the government on Sunday for providing inaccurate information regarding the concentration of radiation in seawater near the plant.

The credibility of its radiation monitoring ability has been brought into question and the utility firm has since stepped up the level of its radiation-detecting activities, to ensure real- time, credible data is available.

As efforts to bring the nuclear crisis, which will enter its fourth week on Friday, under control continue, TEPCO said Tuesday that 60,000 tons of radioactive water is now believed to be flooding the basements of faltering reactor buildings and a labyrinth of underground trenches that connect them.

The massive amounts of leaking radioactive water follows the devastating tsunami ravaging the plant and knocking out its critical cooling functions and the subsequent efforts of workers to douse the over-heating reactors in huge amounts of seawater in a desperate bid to cool them down and avoid a full meltdown.

TEPCO had intentionally dumped 3,430 tons of such low radioactive water into the Pacific Ocean by noon on Tuesday following releasing 11,500 tons of contaminated water into the sea on Monday to free up storage space for extremely radioactive water.

Japan's Nuclear and Industrial Safety Agency said the 60,000 tons of the highly tainted water from three reactor buildings and trenches will be stored in tanks at the units, as well as the plant's regular facility for nuclear waste disposal and an artificial floating island called a megafloat, as well as on U.S. Navy barges and tanks, the agency said.

However the tanks will not ready to be shipped to Fukushima until the end of the month, the safety agency said.

While water containing radioactive iodine-131 more than 10,000 times the legal concentration limit continues to leak from a cracked pit connected to the No. 2 reactor turbine building and flow into the sea, TEPCO continued a third round of efforts to plug the leak, following the failure of previous efforts -- some of which involved using bags stuffed with sawdust and newspaper.

TEPCO believes the radioactive water is coming from the No. 2 reactor's core, where fuel rods have partially melted, but the firm as yet has been unable to determine the route of the radioactive flow.