FUKUSHIMA, Japan - Radiation leaked from Japan's earthquake-crippled nuclear plant on Saturday after a blast blew the roof off, and authorities prepared to distribute iodine to people in the vicinity to protect them from exposure.
The government insisted radiation levels were low because although the explosion severely damaged the main building of the plant, it had not affected the reactor core container.
Local media said three workers suffered radiation exposure at the plant in the wake of Friday's massive earthquake, which sent a 10-meter (33-foot) tsunami ripping through towns and cities across the northeast coast.
Kyodo news agency said more than 1,700 people were killed or missing as a result of the 8.9-magnitude earthquake, the biggest in Japan since records began in the nineteenth century.
Later it said 9,500 people in one town were unreachable, but gave no other details.
The blast raised fears of a meltdown at the power facility, 240 km (150 miles) north of Tokyo, as officials scrambled to contain what could be the worst nuclear disaster since the Chernobyl explosion in 1986 that shocked the world.
However, experts said Japan should not expect a repeat of Chernobyl. They said pictures of mist above the plant suggested only small amounts of radiation had been expelled as part of measures to ensure its stability, far from the radioactive clouds Chernobyl spewed out 25 years ago.
Valeriy Hlyhalo, deputy director of the Chernobyl nuclear safety center, was quoted by Interfax news agency as saying Japanese reactors were better protected than Chernobyl.
"Apart from that, these reactors are designed to work at a high seismicity zone, although what has happened is beyond the impact the plants were designed to withstand," Hlyhalo said.
Japan's Chief Cabinet Secretary Yukio Edano told reporters the nuclear reaction facility was surrounded by a steel storage machine, which was itself surrounded by a concrete building.
"This concrete building collapsed. We learnt that the storage machine inside did not explode," he said.
Edano initially said an evacuation radius of 10 km (6 miles) from the stricken 40-year-old Daiichi 1 reactor plant in Fukushima prefecture was adequate, but then an hour later the boundary was extended to 20 km (13 miles). TV footage showed vapor rising from the plant.
Japanese officials told the U.N.'s atomic watchdog they were making preparations to distribute iodine to people living near nuclear power plants affected by the quake, the Vienna-based agency said. Iodine can be used to help protect the body from radioactive exposure.
The wind at the disabled plant was blowing from the south, which could affect residents north of the facility, Japan's national weather forecaster said, adding the direction may shift later so that it blows from the north-west toward the sea.
The direction of the wind is a key factor in judging possible damage on the environment from radiation.