Panic spread as reports on the crippled Fukushima nuclear plant indicated Wednesday high levels of radiation have leaked at the compound.
In a desperate effort, a Self-Defense Forces chopper tried to carry a bag of water to dump on one overheating location, but had to abort.
On Wednesday, Chief Cabinet Secretary Yukio Edano said the No. 3 reactor's primary containment vessel may have ruptured, although he later withdrew his remark.