TOKYO -- This week's power outage at Japan's tsunami-crippled nuclear plant may have been caused by a rat.Masayuki Ono, spokesman for Tokyo Electric Power Co., the utility that runs the Fukushima Dai-ichi plant, says a 15-centimeter (6-inch) rat was found dead Wednesday near a switchboard. He says the rat may be linked to the power failure, but that more investigation is needed to be sure.Read More... More on Japan