Direct quotes from the article at Kyodo news dated march 15
"The utility said it cannot deny the possibility that the early morning explosion was caused by hydrogen that was generated by a chemical reaction involving the exposed spent nuclear fuel and vapor...
"TEPCO said the problem could develop into a critical ''meltdown'' situation, in which fuel rods melt and are destroyed, emitting massive radioactive materials in the air...."
IT IS TIME TO MONITOR THIS CLOSELY. A LARGE SCALE EXPLOSION WILL BLOW RADIOACTIVE MATERIAL INTO JET STREAM.