A nuclear power plant hit by a strong earthquake in Japan was ordered shut down Wednesday until its safety could be confirmed.

About 13,000 people were staying in schools and other secure buildings in the quake zone, 250 kilometres northwest of Tokyo.
(Koji Sasahara/Associated Press)

Hiroshi Aida, mayor of Kashiwazaki, a town of 93,500 near the quake's epicentre that is home to the plant, ordered operations halted at Kashiwazaki-Kariwa for "safety reasons."

"I am worried," he said. "It would be difficult to restart operations at this time.… The safety of the plant must be assured before it is reopened."

The order came after Japanese officials released a list Tuesday of 50 malfunctions at the Kashiwazaki-Kariwa nuclear power plant.

The malfunctions included fires, water and oil leaks, and pipes knocked out of place by Monday's 6.6-magnitude quake, according to the Tokyo Electric Power Co., the company running the nuclear plant.

Tsunehisa Katsumata, president of Tokyo Electric Power Co., toured the site Wednesday morning and declared it "a mess."

"We will conduct an investigation from the ground up," Katsumata said. "But I think, fundamentally, we have confirmed that our safety measures worked."

Black smoke rises from a burning electrical transformer near one of the Kashiwazaki-Kariwa nuclear plant's four reactors.
(Japan Coast Guard via Kyodo News/Associated Press)

The company said it is still inspecting the plant, which shut down automatically after the quake, and further problems could emerge. Spokesman Kensuke Takeuchi called those discovered so far "minor troubles" and said they pose no threat to people or the environment.

Monday's quake, which killed nine people, injured dozens of others, and left thousands homeless, initially triggered a small fire at an electrical transformer in the sprawling plant. It was announced 12 hours later that the quake also caused a leak of water containing radioactive material.

Officials also said about 100 drums containing low-level nuclear waste fell over at the plant during the quake. They were found a day later, some with their lids open, said Masahide Ichikawa, an official with the local government in Niigata.

Japan's 55 nuclear reactors supply 30 per cent of the country's electricity, and have suffered a long string of accidents and coverups.

Residents crowd shelters

Monday's quake killed nine people in their 70s or 80s — six women and three men — in Japan's northwestern Niigata prefecture. Another 47 were seriously injured.

One person was missing and another 13,000 were staying in schools and other secure buildings in the quake zone 250 kilometres northwest of Tokyo, the Fire and Disaster Management Agency said.

On Tuesday, thousands of residents in Kashiwazaki, the hardest-hit city, huddled in crowded emergency shelters, as others whose houses still stood contended with no power, gas or water services.

Japan's meteorological agency warned residents of potential aftershocks in the coming days after a second strong quake struck in the Sea of Japan off the country's west coast near the Kyoto region just over 12 hours after the first tremor.

Meanwhile, rescue workers searched for survivors amid the rubble of hundreds of homes in the area, as officials warned of potential landslides.

The Defence Ministry dispatched 450 soldiers to the devastated area to clear rubble, search for survivors and provide food, water and toilet facilities.

About 50,000 homes were without water and 35,000 were without gas as of Tuesday morning, local official Mitsugu Abe said. About 27,000 households were without power.

With files from the Associated Press