Authorities said they found high levels of radioactive caesium in sewage sludge near a damaged nuclear plant in north-eastern Japan, news reports said Monday.
The sludge at a treatment centre in Koriyama City, Fukushima Prefecture, had 26,400 becquerels of radioactive caesium per kilogram, Jiji Press reported citing local government officials, dpa reported.
At the centre located some 50 kilometres west of the stricken Fukushima Daiichi nuclear power plant, slag made by reducing the volume of sewage sludge had 334,000 becquerels per kilogram, Jiji said.
Since the March 11 earthquake and tsunami hit the plant run by Tokyo Electric Power Co (TEPCO), it has leaked radiation into the air and sea.
The natural disaster left more than 14,600 dead and some 11,000 missing.
Massive amounts of radioactive substances released by the plant might have flowed into sewage when rain fell, Jiji reported citing local officials.
Some 80 tons of sludge is produced per day at the treatment centre and 10 tons of that amount are transported to a cement company outside the prefecture for recycling, but the prefecture government suspended it on Sunday.
An estimated 500 tons of sludge have been provided to the cement company since the start of the nuclear crisis, the officials said.
Whether they were actually recycled remain to be seen, the officials added.
Local government officials were to examine other treatment facilities in the prefecture while asking the central government to consider how to get rid of sewage sludge contaminated by high-level radiation, Jiji reported.
Meanwhile, TEPCO decided to let workers enter the building of reactor 1 on Monday for their work. The workers were to install a device that can reduce the level of radioactivity by filtering the air in the building, public broadcaster NHK reported.
The density of air contamination in the building would be reduced by 95 per cent, NHK reported citing TEPCO. The company said the device would be installed within a few days.
NHK said it would be the first time for its workers to enter the building since the hydrogen explosion on March 12.