BEIJING - China intensified radiation monitoring in 12 provinces along the coastline after an explosion at a nuclear power plant in northern Japan on Saturday. The blast has led to a radiation leak of unspecified proportions, Japanese officials have confirmed.

The monitoring showed that by Saturday afternoon China had not been affected, the Ministry of Environmental Protection, which oversees the country's nuclear safety issues, said in a statement on its website. All of China's 13 nuclear reactors are operating normally.

The explosion, following a devastating earthquake on Friday, blew off the roof of a building at Fukushima Daiichi 1 nuclear plant, about 240 km north of Tokyo, bringing down walls and causing injuries.