The Japanese government's nuclear safety agency raised the crisis level of the Fukushima Dai-ichi power plant accident from 5 to 7, the worst on the international scale. Kyodo news agency said the government's Nuclear Safety Commission has estimated the amount of radioactive material released from the reactors in Fukushima, northern Japan, reached a maximum of 10,000 terabequerels per hour at one point for several hours, which would classify the incident as a major accident according to the INES scale.

The scale, short for International Nuclear and Radiological Event Scale, is published by the International Atomic Energy Agency and ranks nuclear and radiological accidents and incidents by their severity from 1 to a maximum of 7.