Japanese Prime Minister Naoto Kan has said his government is in a state of maximum alert over the crippled Fukushima nuclear plant. Plutonium has been detected in soil at the facility and highly radioactive water has leaked from a reactor building. Officials say the priority remains injecting water to cool the fuel rods. Mr Kan told parliament the situation at the quake-hit plant "continues to be unpredictable". The government "will tackle the problem while in a state of maximum alert", he said, adding that he was seeking advice on whether to extend the evacuation zone around the plant. Meanwhile National Strategy Minister Koichiro Gemba said the government could consider temporarily nationalising Tepco, the company running the plant.