Tokyo: The Japanese government Saturday said an explosion at a nuclear plant damaged by Friday`s massive earthquake had not affected the reactors. Nor had the explosion at the Fukushima I plant, 240 kilometres north of Tokyo, led to a significant radioactive leak, Chief Cabinet Secretary Yukio Edano told a news conference.
The blast caused the roof of a building housing one of the plant`s three reactors to collapse, injuring four people and raising initial fears of a disastrous meltdown.
There were grim signs that the death toll in the tsunami and quake hit Japan could soar. One report said four whole trains had disappeared Friday and still not been located. Local media reports said at least 1,700 people may have been killed.
The plant`s operators, Tokyo Electric Power Co (TEPCO), said there was no damage to the steel containers in which the reactors are encased.
The government nevertheless extended the evacuation zone to residents living within 20 km of the plant.
Edano had earlier described the situation as "potentially very serious", but called on people to remain calm.
Technicians had been scrambling to reduce pressure in the reactors to prevent a meltdown, after the plant was damaged in Friday`s massive quake, Japan`s Nuclear and Industrial Safety Agency said.
Radioactive caesium has been detected in the vicinity of the plant in north-eastern Japan. The presence of the substance is an indication of a meltdown.
TEPCO managed to depressurise the containers housing the reactors, the agency said, which involved relasing steam that would likely contain radioactive materials.
Technicians encountered difficulties opening a pressure release valve due to high radioactive levels, Kyodo news quoted the nuclear safety agency as saying.
Earlier Saturday, authorities had extended the evacuation zone to residents living within 10 km of the Fukushima I, where the cooling system experienced problems Friday.
But the evacuation had not been completed by early Saturday evening, Kyodo news said.
Meanwhile, residents within three kilometres of a second nuclear plant, Fukushima II located about 11 kilometres from Fukushima I, were also ordered to leave.
The government had held several crisis meetings Saturday to discuss the situation and Prime Minister Kan Naoto toured the disaster area by helicopter.
Radiation measurements inside the Fukushima I plant were 1,000 times higher than normal after the earthquake, Kyodo said.
Authorities were concerned that radioactivity may have escaped the plant due to high pressure inside an overheating reactor.
The magnitude-8.9 quake damaged power supplies and disrupted the reactors` cooling systems. An observation post near the plant`s gate recorded radiation levels eight times higher than normal.
The cooling system for the three reactors at Fukushima II was also out of operation.
Japan`s nuclear authorities earlier informed the Vienna-based International Atomic Energy Agency (IAEA) that they have declared a nuclear emergency situation at Fukushima I and had issued an alert for Fukushima II.
Citing Japanese official reports, the IAEA said the earthquake had cut the off-site power to the Fukushima I plant. Diesel generators meant to provide emergency power for the cooling system were disabled by flooding from the tsunami triggered by the quake and had not yet been restored.
The radioactive cores of the reactors need continued cooling to prevent meltdown.
US Secretary of State Hillary Rodham Clinton Friday said the US Air Force in Japan had transported coolant to the plant.
Rescue operation on
Meanwhile, Japan launched a massive, military-led rescue operation after a giant quake and tsunami killed hundreds of people and turned the northeastern coast into a swampy wasteland.
Prime Minister Naoto Kan said he is sending 50,000 troops for the rescue and recovery efforts following Friday`s 8.9-magnitude quake that unleashed one of the greatest disasters Japan has witnessed.
The official death toll stood at 413, while 784 people were missing and 1,128 injured. Media reports say the toll it is at least 1,600. In addition, police said between 200 and 300 bodies were found along the coast in Sendai, the biggest city in the area near the quake`s epicentre. An untold number of bodies were also believed to be lying in the rubble and debris. Rescue workers had yet to reach the hardest-hit areas.
The atomic emergency came as the country struggled to assess the full extent of the devastation wreaked by the massive tsunami, which was unleashed by the strongest quake ever recorded in Japan off the eastern coast.
More than 215,000 people were living in 1,350 temporary shelters in five prefectures, or states, the national police agency said. Since the quake, more than one million households have not had water, mostly concentrated in northeast.
The full scale of those left homeless was believed to be much higher, with police saying they had not received a tally from Miyagi prefecture, the hard-hit province that is home to Sendai.
Kan said a total of 190 military planes and 25 ships have been sent to the area.
"Most of houses along the coastline were washed away, and fire broke out there," he said after inspecting the quake area in a helicopter. "I realised the extremely serious damage the tsunami caused."
The unstoppable black tide picked up shipping containers, wrecked cars and the debris of shattered homes and crashed through the streets of Sendai and across open fields, forming a mud slick that covered swathes of land.
The tsunami obliterated Rikuzentakata, a coastal city of some 23,000 people, the Fire and Disaster Management Agency said.
More than eight million homes lost power, mobile and landline phone systems broke down and gas was cut to more than 300,000 homes, meaning many Japanese could not heat their dark homes during a tense, cold night.
The military mobilised thousands of troops, 300 planes and 40 ships for the relief effort. An armada of 20 naval destroyers and other vessels headed for the devastated Pacific coast area of Honshu island.
Ports and beaches were temporarily shut and islanders and coastal residents ordered to higher ground up and down Latin America`s Pacific seaboard before the tsunami surge triggered by the 8.9-magnitude earthquake in Japan. But it did little damage.
By the time the tsunami waves travelled across the wide Pacific Ocean and into the southern hemisphere, only slightly higher waters than normal came ashore in Mexico, Honduras and Colombia, Ecuador`s Galapagos Islands, Chile`s Easter Island and Peru and Chile`s mainlands.
Waves as high as 6 feet (almost 2 meters) crashed into South America into early Saturday - in some cases sending the Pacific surging into streets — after coastal dwellers rushed to close ports and schools and evacuated several hundred thousand people.
Nearly 24 hours after the first, massive quake struck just under 400 kilometres (250 miles) northeast of Tokyo, aftershocks were still rattling the region, including a strong 6.8 magnitude tremor on Saturday.
The US Geological Survey said more than 100 aftershocks had hit the area.
Japan sits on the "Pacific Ring of Fire" and Tokyo is in one of its most dangerous areas, where three continental plates are slowly grinding against each other, building up enormous seismic pressure.
The government has long warned of the likelihood that a devastating magnitude-8 quake will strike within the next 30 years in the Kanto plains, home to Tokyo`s vast urban sprawl.
The disaster struck as the world`s third-largest economy had been showing signs of reviving from an economic contraction in the final quarter of last year. It raised the prospect of major disruptions for many key businesses and a massive repair bill running into tens of billions of dollars.
The earthquake was the fifth most powerful to hit the world in the past century. It surpassed the Great Kanto quake of September 10, 1923, which had a magnitude of 7.9 and killed more than 140,000 people in the Tokyo area.
The 1995 Kobe quake caused USD 100 billion in damage and was the most expensive natural disaster in history.