Japan's chief cabinet secretary says a hydrogen explosion has occurred at Unit 3 of Japan's stricken Fukushima Dai-ichi nuclear plant. The blast was similar to an earlier one at a different unit of the facility.Yukio Edano says people within a 12-mile (20-kilometer) radius were ordered inside following Monday's. AP journalists felt the explosion 30 miles (50 kilometers) away.(SCROLL DOWN FOR LIVE UPDATES)Read More... More on Japan Tsunami