Media playback is unsupported on your device Media caption Rupert Wingfield-Hayes reports that the change in severity level is regarded as "significant" 
 
 Japan's nuclear agency has upgraded the severity level of a radioactive water leak at the Fukushima plant from one to three on an international scale. 
 
 Highly radioactive water was found to be leaking from a storage tank into the ground at the plant on Monday. 
 
 It was first classified as a level one incident on the International Nuclear and Radiological Event Scale (Ines). 
 
 But Japan's Nuclear Regulation Authority proposes elevating it to level three on the seven-point scale. 
 
 Media playback is unsupported on your device Media caption Joanna Gosling explains where the leaks are coming from 
 
 Japanese reports say it is a provisional move that had to be confirmed with the IAEA, the UN's nuclear agency. 
 
 This week is the first time that Japan has declared an event on the Ines scale since the 2011 earthquake and tsunami. 
 
 The move was announced in a document on the agency's website and was subsequently approved at a weekly meeting of the regulatory body. 
 
 Shares of plant operator Tokyo Electric Power Company (Tepco) fell as much as 13% to 537 yen as investors worried about the impact of the development. 
 
 'Five-year dose' 
 
 Image caption Workers discovered the water was leaking from a tank on Monday 
 
 The March 2011 tsunami knocked out cooling systems to the reactors at the plant, three of which melted down. 
 
 Water is now being pumped in to cool the reactors but this means that a large amount of contaminated water has to be stored on site. 
 
 What is Ines? Overseen by the UN nuclear agency, the IAEA 
 
 Events are classified at seven levels: Levels 1-3 are "incidents" and Levels 4-7 "accidents" 
 
 In order, the levels are classified as: anomaly; incident; serious incident; accident with local consequences; accident with wider consequences; serious accident; major accident 
 
 To date, two incidents have been classified as level 7 - Chernobyl and Fukushima 
 
 The severity of an event is about 10 times greater for each increase in level on the scale Source: IAEA website 
 
 There have been leaks of water in the past but this one is being seen as the most serious to date, because of the volume - 300 tonnes of radioactive water, according to Tepco - and high levels of radioactivity in the water. 
 
 Japan's Nuclear Regulation Authority (NRA) said it feared the disaster was "in some respects" beyond Tepco's ability to cope. 
 
 "We should assume that what has happened once could happen again, and prepare for more," watchdog chairman Shunichi Tanaka told a news conference. "We are in a situation where there is no time to waste." 
 
 He said Tepco had failed to spot the leak for days - maybe weeks - despite patrols that are supposed to check each storage tank twice every day. Workers had also left a tap open in the safety barrier that surrounds the base of the leaking storage tank. 
 
 That had allowed highly toxic water to trickle away into the ground. Latest reports from the plant suggest some of it may already have reached the nearby Pacific Ocean. 
 
 The BBC's Rupert Wingfield-Hayes in Tokyo says it all adds to the impression that the clean-up operation is riddled with complacency and incompetence. 
 
 A puddle of the contaminated water was emitting 100 millisieverts an hour of radiation, Kyodo news agency said earlier this week. 
 
 Masayuki Ono, general manager of Tepco, told Reuters news agency: "One hundred millisieverts per hour is equivalent to the limit for accumulated exposure over five years for nuclear workers; so it can be said that we found a radiation level strong enough to give someone a five-year dose of radiation within one hour." 
 
 Teams of workers at the plant have surrounded the leaking tank with sandbags and have been attempting to suck up large puddles of radioactive water. 
 
 But our correspondent says it is a difficult and dangerous job. The water is so radioactive that teams must be constantly rotated and it is clear that most of the toxic water has already disappeared into the ground. 
 
 Under the Ines, events have seven categories starting with Level 0 ("without safety significance") and Levels 1-3 denoting "incidents" while Levels 4-7 denote "accidents". 
 
 The triple meltdown at Fukushima two years ago was classed as a level 7 incident, one of only two nuclear events ever rated that highly - along with the 1986 Chernobyl disaster in the former Soviet Union. ||||| TOKYO Japan's nuclear crisis escalated to its worst level since a massive earthquake and tsunami crippled the Fukushima plant more than two years ago, with the country's nuclear watchdog saying it feared more storage tanks were leaking contaminated water. 
 
 The U.N.'s International Atomic Energy Agency (IAEA) said on Wednesday it viewed the situation at Fukushima "seriously" and was ready to help if called upon, while nearby China said it was "shocked" to hear contaminated water was still leaking from the plant, and urged Japan to provide information "in a timely, thorough and accurate way". 
 
 "We hope the Japanese side can earnestly take effective steps to put an end to the negative impact of the after-effects of the Fukushima nuclear accident," China's Foreign Ministry said in a statement faxed to Reuters in Beijing. 
 
 Japan's Chief Cabinet Secretary Yoshihide Suga called the situation "deplorable", and the Nuclear Regulation Authority (NRA) said it feared the disaster - the worst nuclear accident since Chernobyl a quarter of a century earlier - was "in some respects" beyond the plant operator's ability to cope. 
 
 The plant's operator, Tokyo Electric Power Co, or Tepco, has been criticized for its failure to prepare for the disaster and has since been accused of covering up the extent of the problems at the plant. After months of denial, Tepco recently admitted the plant was leaking contaminated water into the Pacific Ocean from trenches between the reactor buildings and the shoreline. 
 
 It said on Tuesday that contaminated water with dangerously high levels of radiation was leaking from a storage tank - the most serious problem in a series of recent mishaps, including power outages, contaminated workers and other leaks. 
 
 The NRA said it was worried about leakage from other similar tanks that were built hastily to store water washed over melted reactors at the station to keep them cool. Water in the latest leak is so contaminated that a person standing close to it for an hour would receive five times the annual recommended limit for nuclear workers. 
 
 A spokesman for the NRA said the agency plans to upgrade the severity of the crisis from a Level 1 "anomaly" to a Level 3 "serious incident" on an international scale for radiological releases. An upgrade would be the first time Japan has issued a warning on the International Nuclear Event Scale (INES) since the three reactor meltdowns at Fukushima in March 2011. Explosions then led to a loss of power and cooling, triggering a maximum INES Level 7 at the plant. 
 
 "HAUNTED HOUSE" 
 
 NRA Chairman Shunichi Tanaka likened the stricken nuclear plant to a house of horrors at an amusement park. "I don't know if describing it this way is appropriate, but it's like a haunted house and, as I've said, mishaps keep happening one after the other," he told reporters. "We have to look into how we can reduce the risks and how to prevent it from becoming a fatal or serious incident." 
 
 He said the NRA would consult with the IAEA about whether it was appropriate to assign a rating to the leakage at the plant. 
 
 "Japanese authorities continue to provide the Agency with information on the situation at the plant, and Agency experts are following the issue closely," Gill Tudor, spokesperson at the Vienna-based IAEA, said in an e-mailed statement. 
 
 "The IAEA views this matter seriously and remains ready to provide assistance on request." 
 
 Each one-step INES increase represents a 10-fold increase in severity, according to a factsheet on the IAEA website. (www.iaea.org/) A Level 3 rating is assigned when there is exposure of more than 10 times the limit for workers, according to the factsheet. 
 
 In an emailed comment, Andrew Sherry, director of the Dalton Nuclear Institute at the University of Manchester, said: "Though serious, this leak is a long way from the Level 7 incident we were facing in 2011. The approach taken by Tepco to drain the tank, pump leaked water to temporary storage, and protect the drainage of contaminated water to ground water, is entirely sensible." 
 
 "This incident highlights the need for an inspection program for these many hundreds of storage tanks, and the need to consider replacing bolted or sealed storage tanks, which were relatively quick to build, with a more robust welded design." 
 
 South Korea's Asiana Airlines Inc said it would cancel charter flights between Seoul and Fukushima city in October due to public concerns over the radioactive water leaks. 
 
 The city, around 60 kms (37 miles) from the nuclear facility and with a population of some 284,000, is a popular destination for golfers and tourists visiting nearby local hot springs and lakes. 
 
 (With additional reporting by Kentaro Hamada, Olivier Fabre and Chris Meyers in TOKYO, Ben Blanchard in BEIJING, Kim Miyoung in SEOUL, Fredrik Dahl in VIENNA and Kate Kelland in LONDON; Writing by Aaron Sheldrick; Editing by Edmund Klamann, Paul Tait and Ian Geoghegan) ||||| >>> good morning. breaking news. japan 's nuclear crisis takes a dire turn. high levels of radiation spewing from the damaged nuclear plant following an explosion at a third reactor and a fire in a fourth. an official is calling it, quote, a very bad scenario as officials work to contain the risk today, tuesday, march 15, 2011 . 
 
 >>> welcome to "today" on this tuesday morning. i'm meredith vieira . 
 
 >> officials in japan are saying the radiation leaking from the crippled nuclear power plant is enough to impact human health . 
 
 >> the big concern is the number 2 reactor which exploded on monday sending more radiation into the air and then a fire at reactor 4 broke out. that one had been shut down for maintenance before the quake. all but 50 employees of the plant have been evacuated. in a nationally televised address japan 's prime minister urged anyone living near the plant who had not already evacuated to seal themselves indoors and warned of the very high risk of more leaks. 
 
 >> you hear the story and i think about the bravery of the 50 people who remain at the plant trying to cool the reactors at great personal risk. 
 
 >> you wonder if they will have to leave as well and then what's going to happen? 
 
 >> what's the outcome of that? 
 
 >> in tokyo , slightly elevated radiation levels have been detected. we'll get the latest on an extremely tense situation straight ahead. 
 
 >> there is a rare piece of good news. rescuers found a 70-year-old woman alive in her home four days after it was swept away by the tsunami. ann curry has details and a closer look at the toll this crisis is taking on people there. let's begin on this tuesday morning with the nuclear crisis. robert bazell , nbc's chief science correspondent, is in tokyo . good morning to you. 
 
 >> reporter: good morning, matt. the nuclear crisis in japan has taken a turn for the worse. many people are saying it's ominous. that explosion in reactor number 4 blew a hole in the cement containment facility allowing radiation to leak. the fire in the other reactor is allowing some radiation to get out. there are several reactors at the fukushima site. one of them in the cement dome. so far the metal cylinder has not broken but radiation is escaping. 
 
 >> the danger seems to have significantly increased over the past couple of days. 
 
 >> reporter: the japanese prime minister naoto kan told people the radiation wasn't a widespread hazard and there was no need to evacuate beyond the 12 miles already established. those leaving have been checked for radiation. all the but the most essential personal nel have been told to leave the site. they offered public apologies. 
 
 >> translator: this is a very poor, very bad scenario. 
 
 >> reporter: satellite photos before and after show the damage. the fire that broke out today is at a reactor that was shut down for maintenance before the earthquake and was not releasing large quantities of radiation. experts agree the total amount of radiation isn't a significant health hazard beyond the area of the reactor. 
 
 >> the amount of radiation that's likely to be released is going to be relatively small compared to an accident like chernobyl. 
 
 >> reporter: it's not chernobyl for sure, but it's worse than mile islan d. 
 
 >> bob, we mentioned that tokyo is 170 miles south of the power plant . i understand there is -- maybe chaos is too strong a word but there are a lot of people who are uneasy in tokyo trying to get out of the country any way they can. is that correc is that correct? are you seeing that? 
 
 >> reporter: mostly foreigners are trying to get out. people aren't leaving tokyo who live here. no one is saying the radiation levels are posing a threat at this time. a lot of foreigners who have the option of getting out are looking at this and saying, well, it's not so bad right now. there has not been this catastrophic leak of radiation everybody fears but let's not wait around for that to happen. if it did nobody's getting out of anywhere. that's the mentality driving a lot of people to book flights and trains to get as far as from here as they can. 
 
 >> robert bazell in tokyo , thank you very much. ||||| 1 of 2. Highly contaminated water leaked from a large storage tank is seen at the H6 area of the contaminated water storage tanks, at Tokyo Electric Power Co. (TEPCO)'s tsunami-crippled Fukushima Daiichi nuclear power plant in Fukushima prefecture in this February 20, 2014 handout photo released by TEPCO. 
 
 TOKYO (Reuters) - The operator of Japan's Fukushima nuclear plant said on Thursday that 100 metric tons of highly contaminated water had leaked out of a tank, the worst incident since last August, when a series of radioactive water leaks sparked international alarm. 
 
 Tokyo Electric Power Co told reporters the latest leak was unlikely to have reached the ocean. But news of the leak at the site, devastated by a 2011 earthquake and tsunami, further undercut public trust in a utility rocked by a string of mishaps and disclosure issues. 
 
 "We are taking various measures, but we apologize for worrying the public with such a leak," said Masayuki Ono, a spokesman for the utility, also known as Tepco. 
 
 "Water is unlikely to have reached the ocean as there is no drainage in that tank area." 
 
 Tepco said water overflowed from a large storage tank at the site late on Wednesday after a valve had remained open by mistake and sent too much contaminated water into a separate holding area. 
 
 A worker patrolling the area, around 700 meters from the ocean, spotted drips of water leaking through a drain attached to the side of the tank. 
 
 The utility has been harshly criticized for its response to the three nuclear meltdowns following the quake and tsunami at the plant, 220 km (130 miles) north of Tokyo. 
 
 A nuclear regulatory official last week said Tepco delayed release of record-high measurements of strontium-90 in groundwater despite repeated requests by the regulator. 
 
 Initial measurements of the latest incident showed the leaked water had a reading of 230 million becquerels per liter of beta-emitting radioactive isotopes, including strontium 90. 
 
 That level is almost equal to that recorded in last year's leak of 300 metric tons of contaminated water, deemed a "serious incident", or level three, on the seven-point international scale for radiological releases. 
 
 The legal limit for releasing strontium 90 into the ocean is 30 becquerels per liter. 
 
 (Additional reporting by Kentaro Hamada; Editing by Dominic Lau and Ron Popeski)
– With Fukushima's radioactive leak now leakier, Japan's nuclear agency plans to up the alert level of the problem from a one to a three, reports the BBC—that's from an "anomaly" to a "serious incident," per the UN's International Nuclear and Radiological Event Scale. For some perspective, the 2011 meltdown was a level seven, or a "major accident." Still, if the UN's nuclear agency OKs the upgrade, this would be the first time Japan has issued a warning since the original meltdown, notes Reuters. Since the new leak was found, teams have been surrounding the affected tank with sandbags and trying to vacuum up puddles of radioactive water. But most of the water has already been absorbed into the ground, reports the BBC, and the chairman of the Japanese agency fears more tanks will follow suit soon. "We should assume that what has happened once could happen again, and prepare for more," he says, per the AP. "We are at a situation where there is no time to waste."