North Korea's test on Wednesday angered both the United States and China, which was not given prior notice, though the U.S. government and weapons experts doubt the North's claim that
the device it set off was a hydrogen bomb.
               
Environment ministry of China claimed today in a statement that over 500 people had been involved in monitoring for radiation, including about 350 people along the border itself, along with 37 fixed monitoring stations and 14 mobile ones.
               
It showed pictures on its website of a radiation monitoring vehicle driving along a snowy road along the border, and an official standing in the snow looking at technical equipment.

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