Japan's crippled Fukushima nuclear plant has been facing a new "emergency" that the plant's operator is not sufficiently addressing, a nuclear watchdog said.
The contaminated groundwater seeping into the ocean breached an underground barrier and was rising towards the surface, Shinji Kinjo, head of a Nuclear Regulatory Authority (NRA) task force, told Reuters news agency.
New measures are needed to stop the water from flowing into the sea.
Rising groundwater is the latest problem for TEPCO, operator of the nuclear plant which has been criticised for a slow improvised response and faulty disclosure ever since the giant March 2011 earthquake and tsunami wrecked the facility.
The regulatory task force overseeing Fukushima said "new measures are needed to stop the water from flowing into the sea''.
Masashi Goto, a retired nuclear engineer who worked on several TEPCO plants, said the company had not been proactive in resolving the contamination crisis.
He said the current situation was more than TEPCO could handle.
It was not immediately clear how much of a threat the possible increase in contaminated groundwater could cause.
In the weeks following the 2011 disaster that destroyed the plant, the Japanese government allowed TEPCO to dump tens of thousands of tonnes of contaminated water into the nearby Pacific Ocean in an emergency move.
The toxic water release was heavily criticised by neighbouring countries as well as local fishermen and the utility has since promised it would not dump irradiated water without the consent of local townships.