Japan's Chief Cabinet Secretary Yukio Edano on Monday railed against owner and operator of the troubled Fukushima Daiichi nuclear power plant Tokyo Electric Power Co.(TEPCO) for providing hugely inaccurate data to the government on the concentration of radioactive substances in one of the reactor's fuel pools.

Edano, Japan's top government spokesperson, admonished the beleaguered utility after they retracted a statement made earlier Monday that the concentration of radioactive substances detected in the pool at the No. 2 reactor was 10 million times higher than usual.

"The erroneous reading given by Tokyo Electric Power Co. is completely unacceptable," Edano said at a news conference.

TEPCO later corrected itself saying the reading was actually 100,000 times higher than usual, reading more than 1,000 millisieverts per hour at the surface of the flooded No. 2 reactor 's turbine building.

The government's Nuclear and Industrial Safety Agency also slammed the utility saying that such errors are further eroding the government's and the public's trust in TEPCO's assessments.

With reference to the surge in radiation detected in the No. 2 reactor's fuel pool for the third straight day, Edano said that water flooding the basement of the reactor's building had become irradiated due to melted fuel rods.

"The radiation seems to have come from fuel rods that temporarily melted down and came in contact with the water used to cool the reactor. Steam may have condensed carrying water from within the containment vessel," he said.

The Chief Cabinet Secretary added that it was essential to ensure the contaminated water does not leak into the soil or the sea and said that the airborne radiation in the No. 2 reactor building is predominantly contained within the structure.

Due to the escalating crisis at the power plant located 240 kilometers northeast of Tokyo, Edano said that residents living within the 20 kilometer evacuation zone around the stricken facility should not return home for the time being.

His comments came following local media reports saying that some residents had started returning home to collect possessions.

"It is very likely that within 20 km from the plant is contaminated and there is a big risk to human health at the moment, " Edano said, adding that residents should remain outside the evacuation zone until told otherwise by the government.

TEPCO on Monday continued with work to remove contaminated water from four of the plant's reactors by pumping the water from the basements into the reactors' turbine condensers for storage.

But the government's nuclear safety agency said Monday that radioactive iodine-131 more than 1,000 times above the maximum level was detected Sunday in a seawater sample taken around 1.5 kilometers north of the drainage outlets of the plant's four most troubled reactors, suggesting the crisis is still far from over and is spreading.

Three workers have been hospitalized following exposure to radiation at the faltering plant since work began to restore cooling systems following the March 11 earthquake and tsunami that devastated the region and damaged the plant.

A total of 19 workers have been exposed to radiation exceeding 100 millisieverts at the plant -- the previous legal limit before the government raised it to 250 millisieverts.