The Associated Press reported within the hour that workers again had to be evacuated from Fukushima Daiichi:
What caused the smoke to billow first from Unit 3 at the Fukushima Dai-ichi plant and later from Unit 2 is under investigation, nuclear safety agency officials said. Still, in the days since the March 11 earthquake and tsunami wrecked the plant’s cooling systems, both reactors have overheated and seen explosions. Workers were evacuated from the area to buildings nearby, though radiation levels remained steady, the officials said.
More as things develop.