HARBIN - A cautious calmness prevails in four counties of Northeast China's Heilongjiang province, where the first traces of radioactive iodine were detected on Saturday.

Officials confirmed a rise in radiation -- an infinitesimal amount of radioactive iodine-131, one-hundred-thousandth beyond normal background radiation levels -- was found in the atmosphere of Dongning, Raohe, Hulin and Fuyuan counties, which are about 1,100 kilometers from Japan's Fukushima Daiichi nuclear plant.

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Liu Changming, director of Fuyuan county government's general office, told China Daily on Sunday that locals in Fuyuan are staying calm because of their "distance from the radiation source and clear media message saying the amount is harmless".

He said the relevant authorities in the county, including the environmental protection, transport and health bureaus, held an ad hoc meeting on Sunday morning to prepare an emergency plan after learning about the rise in radioactive materials.

County government officials from Raohe and Hulin counties also told China Daily that local people had taken the news calmly.

The Ministry of Health said on its official website on Sunday the situation poses no risk to public health as the increase is negligible.

As the monitoring work continues, the government will release information about the situation in a timely manner, the ministry said.

According to the Ministry of Environmental Protection, the monitoring of 42 major cities in China by 4 pm on Sunday showed the "Japanese nuclear incident does not affect the country's environment and public health".

However, the four counties in Heilongjiang are not included in the ministry's report chart. Monitoring station officials from the ministry declined to tell China Daily the latest radiation levels in the four counties.

But local officials remain optimistic.

"The small amount of radioactive material is not a big concern. The government will alert us whenever it's necessary, but not now," said Li Fangjun, a Raohe government official in charge of public complaints.