Prime Minister John Key has confirmed that two New Zealanders in a helicopter which landed 40 kilometres away from the Fukushima nuclear plant in Japan were exposed to low levels of radiation.
Mr Key says they have been through a decontamination process and at this stage there are no concerns for their health.
Two of four Australians also in the helicopter also had low-level exposure.
One of the New Zealanders is a member of an Urban Search and Rescue team there to help with the earthquake and tsunami disaster, and one is a translator.
Their helicopter landed 20 kilometres outside the 20-kilometre exclusion zone around the crippled plant, where several explosions and fires have occurred since Friday's earthquake.
Mr Key says the crew were scoping the area where they were going to work, but ice on the blades forced them to land at an airport.
They then had to use ground transport to return to base; small amounts of radioactive material were subsequently discovered on some of their boots.
The Fire Service says it's monitoring radiation levels as its Urban Search and Rescue team works alongside Japanese civil defence workers in the devastated town of Minamisanriku.
The 48-strong group is scouring the towering piles of wreckage for survivors but so far no one has been found alive.
Team leader Jim Stuart-Black says the members of the group who landed in a helicopter near the Fukushima power plant were all checked for exposure when they arrived back at their base.
He says the contamination levels weren't high, and everyone has been advised there is no danger involved.
Travel advisory updated
The Ministry of Foreign Affairs and Trade has updated its travel advisory for Japan to include advice from New Zealand's National Radiation Laboratory on the nuclear situation.
It says New Zealanders in Japan should not travel to the area within a 20-kilometre radius of the Fukushima power plant.
If they are between 20 and 30 kilometres from the facility, it says, they should follow official advice to stay indoors, close doors and windows and not use ventilation.
The laboratory says people outside the affected areas are extremely unlikely to be contaminated and the health risks are negligible.