Steam has been seen rising from a reactor building at Japan's tsunami-hit Fukushima nuclear plant, the plant operator said Thursday.
The Tokyo Electric Power Company (Tepco) said there was no emergency situation, and there were no signs of increased radiation in the area, BBC reported.
It said it was investigating what was causing the steam at the damaged No.3 reactor building.
The plant was crippled by a massive earthquake and tsunami in 2011. The tsunami knocked out cooling systems to the reactors, three of which melted down. The plant has since seen a series of water leaks and power failures.
Water is being pumped into the reactors to cool them, but that has left Tepco with the problem of storing the contaminated waste water.
A worker first noticed the steam after reviewing camera footage taken of the building, Tepco said.
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The reactor water injection and the cooling of the spent fuel pool were "continuing stably", the operator said. There were also no significant change in the temperature of the reactor.
This is the latest in a series of problems that the plant has faced in recent months.
Last week, a sharp increase in radioactive cesium was detected in groundwater 25 metres from the sea. In June, radioactive water was also found to be leaking from a storage tank.