As of the sampling done four days ago, the radiation fallout level has spiked up to twenty six times its average level since the past year in Japan. The reading indicates 100.4 MBq/Km2. The average reading was at 3.85 MBq/Km2 until 26th April. The reason behind this sudden climb is not known as of yet. 

The leak is suspected from the radioactive waste water from the water storage ponds at Fukushima I Nuclear Power Plant. The amount of radioactive material in the water sample taken from Pond No. 1 on 27th April has led to this discovery.
As per air samples taken by the United States Environmental Protection Agency at eighteen different collection points in the Pacific States, the average level of radioactivity in the air has also spiked to  more than seven times the normal levels.