Smoke ascends over an industrial area as flames are seen in Sendai, northern Japan on Saturday as authorities braced for a possible meltdown at a nuclear reactor. The second hydrogen explosion in three days rocked the Fukushima power plant on Monday morning, injuring 11 workers. The blast occurred at the Unit 3 reactor, two days after an explosion at Unit 1. "First I was worried about the quake," Kenji Koshiba, a construction worker who lives near the plant, told the AP. "Now I'm worried about radiation." A set of fuel rods at a separate reactor in the complex were exposed after losing its ability to cool down, the AP said citing officials. The meltdowns increase the chances of a possible radioactive leak while the exposure raises the risk of overheating and a possible third explosion at the plant. Nearly 80,000 residents were evacuated from the area around the power plant on Monday, according to the Kyodo news agency, AP reported.