At least 160 people were being tested for radiation exposure on Sunday after tens of thousands of residents were evacuated in the wake of an explosion at a nuclear reactor damaged by Friday's massive quake and tsunami.
According to Japan's Nuclear and Industrial Safety Agency (NISA), one group of about 60 people were thought to have been exposed while waiting to be picked up by helicopter at the Futaba high school grounds.
A further 100 people evacuated by bus from Futaba-machi were also being tested, the agency said. Authorities warned residents to keep windows and doors closed.
Of the 100 people evacuated by bus, nine had been tested and one had been shown initially with a radiation count of 100,000cpm -- a level at which experts say a person needs to be decontaminated. Results were still to be released from the helicopter evacuees.
The other eight people showed counts ranging between 18,000cpm and 40,000cpm. It was not known if these people would also need to undergo decontamination.