21:00 JST March 15: Japan faced a potential catastrophe on Tuesday after a quake-crippled nuclear power plant exploded and sent low levels of radiation floating toward Tokyo, prompting some people to flee the capital and others to stock up on essential supplies. Prime Minister Naoto Kan urged people within 30 km (18 miles) of the facility -- a population of 140,000 -- to remain indoors amid the world's most serious nuclear accident since the Chernobyl disaster in Ukraine in 1986. Officials in Tokyo -- 240 km (150 miles) to the south of the plant -- said only minute levels of radiation had been detected so far in the capital, which were "not a problem." Radiation levels in the city of Maebashi, 100 km (60 miles) north of Tokyo, and in Chiba prefecture, nearer the city, were up to 10 times normal levels, Kyodo news agency said. Foreign experts disagreed on whether this was harmful or not. Around eight hours after the explosions, the U.N. weather agency said win...