A Chinese environmental monitoring team has not found radioactive substances in the East China Sea from samples collected immediately following the first explosion at a nuclear power plant on Japan's east coast.

Initial test results of the sampled water showed no abnormal signs, said Xu Ren, director of the environmental monitoring center of the State Oceanic Administration's East China Sea Branch.

Further tests will be conducted while a second batch of monitoring boats will depart Tuesday to collect new samples from the East China Sea, Xu said.

The samples were collected from monitoring spots located at 1,500-2,500 km away from Japan's Fukushima No. 1 nuclear power plant. At least two hydrogen blasts have hit the plant's nuclear reactors since a magnitude 9 earthquake struck northeast Japan last Friday, triggering a tsunami and causing widespread devastation.

Japan's nuclear safety agency has urged residents living around the Fukushima No.1 nuclear power plant to stay indoors and avoid exposure to possible radioactive substances.