A top power company official defended safety standards at an earthquake-ravaged nuclear plant Wednesday, even as the company said a radioactive leak was bigger than first reported and came under international pressure for details. The mayor of nearby Kashiwazaki city ordered the facility to shut down until its safety can be confirmed, escalating the showdown over a long list of problems at the Kashiwazaki-Kariwa plant, the world's largest in terms of power output capacity. The International Atomic Energy Agency meanwhile pressed Japan to undertake a transparent and thorough investigation of the accidents to see if there are lessons that can be applied to nuclear plants elsewhere in the world. Adding to the urgency was new data from aftershocks of Monday's deadly 6.8-magnitude quake suggesting a fault line may run underneath the mammoth power plant. Tsunehisa Katsumata, president of plant operator Tokyo Electric Power Co., visited the site Wednesday morning, declaring it "a mess." The previous evening, his company released a list of dozens of problems triggered by the quake. A tour later given to Japan's Communist Party chief, Kazuo Shii, and a handful of reporters revealed widespread damage across its sprawling compound, including large cracks in roads, toppled concrete fences and buckled sidewalks. Repair workers climbed over a three-story transformer building, which was charred from top to bottom in a fire that burned for two hours Monday. "This is unforgivable," Shii told TEPCO Deputy Superintendent Masakazu Minamidate. "You say there's no leak before you really know. ... The delay in information was especially inexcusable." Katsumata earlier apologized for "all the worry and trouble we have caused." "It is hard to make everything go perfectly," he said. "We will conduct an investigation from the ground up. But I think fundamentally we have confirmed that our safety measures worked." TEPCO, Japan's largest power company, said the quake was stronger than planned for at the seven-reactor plant in the northern prefecture of Niigata. But none of the problems posed serious threats to people or the environment, it said. Still, the plant suffered a fire, broken pipes, water leaks and spills of radioactive waste. After Katsumata's plant tour, TEPCO announced that a leak of radioactive water into the Sea of Japan was actually 50 percent bigger than announced Monday night. But the levels were still well below danger levels, it said. The size of radioactive leak was 90,000 becquerels, not 60,000, TEPCO said in a statement. "We made a mistake in calculating the amount that leaked into the ocean. We apologize and are making a correction," the statement said. Spokesman Jun Oshima said the amount was still "one-billionth of Japan's legal limit." Still unconvinced was Hiroshi Aida, the mayor of Kashiwazaki, a city near the epicenter that is home to the plant and 93,500 people. He ordered operations at the plant to be halted Wednesday 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." TEPCO had already come under fire for delays in reporting troubles, including the fire at an electric transformer and leaks of water containing radioactive material, but the lengthy list of problems released more than a day after the temblor stoked further concerns about the safety of nuclear power in this quake-prone country. Speaking in Malaysia, IAEA chief Mohamed ElBaradei said a thorough review was key and offered to have his Vienna-based agency pull together global experts. "It doesn't mean that the reactor structure or system has been damaged," ElBaradei said. "I would hope and I trust that Japan would be fully transparent in its investigation of that accident. The agency would be ready to join Japan through an international team in reviewing that accident and drawing the necessary lessons." Chief Cabinet Secretary Yasuhisa Shiozaki urged TEPCO to be more transparent in reporting problems, especially those that may impact the public. "We want the report itself to be honest and we want it quickly," he said. Similar concern was echoed across the country, which depends on 55 nuclear power plants for about 30 percent of its electricity needs. "This was a relatively new nuclear power plant, but what would have happened if it was at an old plant? We need to thoroughly review what happened and learn the lesson from this case," national daily Asahi said in an editorial Wednesday. TEPCO spokesman Hiroshi Itagaki said aftershock data indicate a fault under the ocean floor near the plant. While it was unclear how close the line came to the plant, Meteorological Agency official Osamu Kamigaichi said it may stretch under its grounds. The plant lies only 19 kilometers (12 miles) from the epicenter of the quake, just off the nearby coast of the Sea of Japan, TEPCO said. That temblor killed nine people, damaged hundreds of buildings, buckled roads and severed utilities. Kashiwazaki-Kariwa eclipsed a nuclear power station in Canada as the world's largest power station when it added its seventh reactor in 1997. It generates 8.2 million kilowatts of electricity, but has been plagued with mishaps. In 2001, a radioactive leak was found in a turbine room. The plant's safety record and its proximity to a fault line prompted residents to file lawsuits claiming the government had failed to conduct sufficient safety reviews when it approved construction of the plant in the 1970s. But in 2005, a Tokyo court threw out a lawsuit filed by 33 residents, saying there was no error in the government safety reviews.