Levels of radioactive materials in the Chinese mainland remained harmless as the quake-induced Japanese nuclear incident has been upgraded to the top level of severity, according to China's National Nuclear Emergency Coordination Committee Tuesday.

As of 10:30 am Tuesday Beijing Time, no obvious changes in the situation have been observed and readings from on-site radiation monitoring posts at the quake-damaged Fukushima Daiichi Nuclear Power Plant in Japan remain stable, according to the daily statement, quoting the International Atomic Energy Agency's latest report.

Earlier Tuesday, Japan raised the rating of its nuclear disaster to the most serious level on a UN international scale of atomic crises, the first time the top ranking has been adopted since the 1986 Chernobyl disaster in the former Soviet Union.

"The adjustment of the severity level won't affect our previous opinion, which is that the Fukushima nuclear incident won't harm China's environment or public health," said the statement.

According to the document, no obvious change has been found on the levels of radioactive material in the environment and food samples in the Chinese mainland.

A sample survey showed no abnormality in drinking water, the statement said, adding that no protective measures need to be taken against contamination from these materials.