Japan's nuclear crisis verged toward catastrophe on Tuesday after an explosion damaged the vessel containing the nuclear core at one reactor and a fire at another spewed large amounts of radioactive material into the air, according to statements from Japanese government and industry officials.

In a brief morning address to the nation Tokyo time, Prime Minister Naoto Kan pleaded for calm, but warned that radiation had already spread from the crippled reactors and there was "a very high risk" of further leakage.

Engineers at the plant, working at tremendous personal risk, on Tuesday continued efforts to cool down the most heavily damaged unit, reactor No. 2, by pumping in seawater. The fourth reactor had been turned off and was under refurbishment for months before the earthquake and tsunami hit the plant on Friday.

Published Date : Wednesday, 16/3/2011 4:14 PM IST