New Zealanders may need to leave Japan

Foreign Affairs officials are considering whether to advise New Zealanders to leave Japan, as the nuclear crisis deepens in the quake-stricken nation.

The magnitude 9.0 earthquake and tsunami on Friday cut power to the Fukushima nuclear plant, causing explosions and fires that yesterday released a cloud of potentially life-threatening radiation.

People within a 20km exclusion zone have been advised to stay indoors and a 30km no-fly zone was in place around the stricken plant.

More than 1800 New Zealanders are registered as being safe and well in Japan, but the Ministry of Foreign Affairs and Trade still has serious concerns about one New Zealander missing in the affected area.

Foreign Minister Murray McCully this morning said they were seeking further information on that person.

"We're also assessing whether we should give a generalised warning to New Zealanders this morning as to whether they should get further away than the official evacuation zone, or whether we should suggest to people that they should leave completely," Mr McCully told Radio New Zealand.

"That's not something we'd do lightly, but we are looking at that situation."

Japanese authorities have advised the nuclear crisis was slowly being stabilised, but Mr McCully said media reports had painted "a different story".

In an apparently desperate measure, Japanese police would try to cool one of the reactors with water cannons normally used to control riots.

"We need to make our own assessment, and as you'll appreciate that's difficult but it's something we're doing in association with others," Mr McCully said.

Australia yesterday advised its nationals to consider leaving Tokyo and quake-hit areas, while Britain advised against all nonessential travel to Tokyo and northeastern Japan.

Meanwhile, two New Zealanders sent to Japan to assist in the recovery effort tested positive for low levels of radiation.

Prime Minister John Key said yesterday that a Fire Service urban search and rescue team member and an interpreter had been in a Black Hawk helicopter forced to land 20km from the exclusion zone because of ice on its blades.

The men, along with four Australians, were tested for radiation contamination when they arrived back at their base.

The two New Zealanders and two of the Australians had very low levels of radiation contamination on them, Mr Key said.

The group had been through a decontamination process, and Mr Key said it was not believed that they were suffering any health risks.

They would remain in Japan while their relevance and their role there was continuously being assessed.