"Extremely low levels" of radioactive iodine have been detected in the air over all the provincial-level regions but Tibet Autonomous Region on the Chinese mainland, but the material poses no threat to public health or to the environment, said an official statement issued on Friday.

According to a daily statement issued by China's National Nuclear Emergency Coordination Committee, low levels of radioactive isotope iodine-131 have also been detected in the air above the East China Sea, but the amount of radiation given off by the material is below one hundred-thousandth of the average annual exposure level to natural radioactive sources such as rocks, soil, food and the sun.

The material is believed to have drifted to China by air from the quake-damaged Fukushima Daiichi Nuclear Power Plant in Japan.

No protective measures need to be taken against contamination from the material, said the statement.

The committee's conclusion was based on monitoring and analysis results from the Beijing-based Regional Specialized Meteorological Center affiliated with the World Meteorological Organization and the International Atomic Energy Agency, the State Oceanic Administration and the Ministry of Environmental Protection, according to the statement.

Low levels of iodine-131 were first detected in northeastern China's Heilongjiang Province on March 26.