The company that runs a Japanese nuclear power plant destroyed by a tsunami two years ago said on Tuesday it was losing faith in temporary storage pits for radioactive water - but it doesn't have anywhere else to put it.
Tokyo Electric Power Co (Tepco) said it had found a new leak at one of the pits at the Fukushima Daiichi plant.
Three out of seven storage pits are now leaking, compounding clean-up difficulties after the world's worst nuclear crisis in 25 years.
"We cannot deny the fact that our faith in the underwater tanks is being lost," Tepco general manager Masayuki Ono told a hastily arranged news conference.
"We can't move all the contaminated water to above ground (tanks) if we opt not to use the underground reservoirs," Ono said. "There isn't enough capacity and we need to use what is available."
A tsunami crashed into the power plant north of Tokyo on March 11, 2011, causing fuel-rod meltdowns at three reactors, radioactive contamination of air, sea and food and triggering the evacuation of 160,000 people.
The fresh leak was found in the No. 1 storage pool where contaminated water from the leaking number 2 pit was being transferred. Tepco has halted the transfer of the contaminated water.
Ono said on Monday Tepco did not have enough tank space should it need to move the water out of the storage pits, which were dug into higher ground away from the damaged reactors and lined with waterproof material. The company has stepped up construction of the sturdier tanks, he said.