Environmental watchdogs along China's east coast ramped up monitoring efforts after radiation leaked from Japan's quake-damaged Fukushima No. 1 Nuclear Power Plant reached dangerous levels on Tuesday.

Initial environmental monitoring had not found any "abnormal" levels of radioactive substances by 4 p.m. Tuesday, the Ministry of Environmental Protection said in an updated statement.

Monitoring stations in Shanghai as well as those in the eastern provinces of Heilongjiang, Liaoning, Shandong, Jiangsu, Zhejiang and Fujian were ordered to conduct around-the-clock surveillance of radioactive substances in the air and sea water.

In Shanghai, authorities said they are preparing to inform the public of the dangers of radioactive substances and precautionary measures to take in case of contamination.

In Jiangsu, authorities said the Tianwan nuclear plant, located in a coastal city some 500 sea miles from the coast of Japan, has not been affected by the destructive earthquake and subsequent tsunami.

In Liaoning, inspectors went to the province's airports to check whether goods transported from Japan were contaminated by radioactive substances. (Nuclear experts called on the public to remain calm and learn about what precautionary measures to take if nuclear leaks were reported.

Meteorological experts say west-blowing winds will prevail in the area between Shanghai and Japan's Fukushima over the coming week, making Shanghai's air less likely to be tainted by radioactive substances leaked from the nuclear plant.

Experts also say rains forecasted in Shanghai and adjacent areas in the coming days are not related to cloud movements from Japan and local residents are not advised to stay indoors.

An explosion was heard early Tuesday morning at the No. 2 reactor and another hydrogen blast broke out in the building housing the No. 4 reactor at Fukushima No. 1 Nuclear Power Plant which had been crippled by Friday's devastating magnitude 9.0 earthquake, the government said.

The Japanese government on Tuesday said levels of radiation released by damaged reactors at the nuclear power plant were high enough to threaten human health in the immediate area.

Japan's nuclear safety agency has urged residents living around the damaged nuclear power plant to stay indoors and avoid exposure to possible radioactive substances.

(Xinhua News Agency March 15, 2011)