BEIJING: Authorities in northeast China have detected extremely low levels of radioactive iodine in the air which they say is from the stricken nuclear power plant in Japan, state media and officials said.

The environment ministry said Saturday that monitoring stations in Heilongjiang province had found “infinitesimal” traces of radioactive iodine-131, but the public did not need to take “protective measures”.

China’s National Nuclear Emergency Coordination Committee said the radioactive iodine had been emitted by the nuclear power facility in Fukushima, which was crippled by a massive quake and ensuing tsunami two weeks ago.

But the committee said “public health and the environment remain unaffected by radioactivity” released by the plant, the official Xinhua news agency reported.

On Friday, China banned imports of several food products from Japan and stepped up checks on a host of other goods amid fears of contamination.

The ban was announced after the country's safety watchdog reported finding elevated radiation levels on two Japanese travellers after they arrived in eastern China from Tokyo.

The General Administration of Quality Supervision, Inspection and Quarantine said it had also detected radiation on a Japanese merchant vessel that berthed in the southeastern port city of Xiamen on Monday.

The 9.0-magnitude quake and monster waves which struck Japan on March 11 have devastated large areas of the country, damaged the plant on its eastern coast and stoked contamination fears both at home and abroad.

In the wake of the twin disasters, many Chinese stores reported panic-buying of salt, with consumers mistakenly believing that its iodine could protect against radiation poisoning.