Two New Zealand rescue workers in Japan have had to be decontaminated after they were found to have been exposed to radiation after landing at the Fukushima airport.

The airport is 20 kilometres outside the exclusion zone mandated in the wake of damage to a nuclear power plant from the magnitude 9.0 earthquake that hit Japan on Friday.

Prime Minister John Key this afternoon said two New Zealanders - one USAR (Urban Search and Rescue) member and one translator - were on a Blackhawk helicopter with some Australians which had to set down at Fukushima airport because of ice on the chopper blades.

They then had to use ground transportation and high levels of radiation were picked up on the boots of the New Zealanders.

After the men returned to the joint Australia/New Zealand base - about 100km from the exclusion zone - they were tested for radiation exposure and "very low levels" were found on the two New Zealanders and two of the Australians.

"They went through a decontamination process. We do not believe they are suffering any health risks, nor do we believe they are at any risk.

"We are in constant contact with the National Radiation Laboratory and we are quite comfortable with their position. Nevertheless, we have taken every cautionary step you would expect us to."

He said the men were flying to scan the area in which they expected to be working as part of the rescue effort.

There were no plans for the men to return home to New Zealand following the incident.

Similarly, Australian Prime Minister Julia Gillard told media the Australian rescue workers were not expected to be at any risk.

"The clear advice to me is that these two personnel are safe and well," she said.

Ms Gillard said the International Atomic Energy Agency had advised her that health risks, from exposure to the radiation, was low to negligible.

"Our nuclear experts advise that there is a small chance of contamination at very low levels for Australians who were in the Fukushima area," she said.

But concerned Australians returning from Japan are advised to visit their doctor, Ms Gillard said.

Ms Gillard said 145 Australians were unaccounted for in quake-affected areas.

"Our consular staff in Japan have not been able to make contact with them yet," she said.

"What we are trying to do is contact them and make sure they are safe."

Meanwhile, Japanese media reports efforts to find survivors and recover bodies from one of the most devastated areas of Japan have been bolstered by New Zealand Urban Search and Rescue (USAR) workers.

The USAR team has arrived at the town of Minamisanriku, which was nearly completely destroyed in Friday's tsunami, NHK news reported.

It has been joined by other teams from countries including Australia and Sweden, the agency says.

Japanese officials have said more than half of the Minamisanriku's 17,000 residents are missing.

Of all its buildings, only three have been left standing - the hospital, a wedding store and a school - despite the town's location several kilometres from the coast.

Fire Service national manager of special operations and team leader Jim Stuart-Black yesterday said he, the Australian USAR taskforce leader and Japanese emergency officials were discussing their planned operations in tsunami-affected areas.

"The team morale is great and we are very focused on the work ahead. We are setting up our base of operations and preparing to begin searching for survivors," he said.

The team was "well aware" of the nuclear power plant issues emerging 130km south of their base, he said.

"We have good information on the situation and are being kept well informed of all developments.

"We also have our own equipment and are constantly monitoring the atmosphere. The radiation levels here are the normal background levels."

- with NZ Herald staff