An explosion rocked one of Japan's nuclear power plants
Saturday, causing a portion of a building to crumble, sending
white smoke billowing into the air and prompting Japanese
officials to warn people in the vicinity to cover their mouths
and stay indoors. In what may become the most serious nuclear
power crisis since the Chernobyl disaster, the explosion
followed large tremors at the Fukushima Daiichi No. 1 reactor
Saturday afternoon, injuring four workers who were struggling to
get the quake-stricken unit under control. Earlier, Japan's
Nuclear and Industrial Safety Agency (NISA) had warned that the
reactor, whose cooling system had been crippled by the giant
earthquake Friday, could be nearing a meltdown and that two
radioactive substances, cesium and radioactive iodine, had
already been detected nearby. The full extent of the blast
remained unclear, but footage on Japanese television showed that
the walls of the building housing the reactor crumpled, leaving
a skeletal metal frame, according to the Associ