TOKYO - Japanese officials say they believe a hydrogen explosion has occurred at Japan's stricken Fukushima Dai-ichi nuclear plant, similar to an earlier one at a different unit in the facility.
A massive column of smoke was seen belching from the plant's No. 3 unit Monday. The reactor had been under emergency watch for a possible explosion as pressure built up there following a hydrogen blast Saturday in the facility's Unit 1.
Officials have been racing stave off multiple reactor meltdowns after a devastating quake and tsunami incapacitated the Fukushima plant.
More than 180,000 people have evacuated the area, and up to 160 may have been exposed to radiation.