Japan's massive earthquake caused a power outage that disabled a nuclear reactor's cooling system, triggering evacuation orders for about 3,000 residents as the government declared its first-ever state of emergency at a nuclear plant.
Japan's nuclear safety agency said pressure inside one of six boiling water reactors at the Fukushima Daiichi plant had risen to 1.5 times the level considered normal. To reduce the pressure, slightly radioactive vapor may be released. The agency said the radioactive element in the vapor would not affect the environment or human health.