Radiation level in the 80-kilometer zone around the imploded Fukushima nuclear plant in Japan has decreased 23 percent between November and June, NHK television reported on Saturday.
The data comes from Japan's Science and Technology Ministry, which took 140,000 samples on the ground and in the air around the disaster-hit plant.
The natural decline in radiation levels is estimated to be 14 percent. The ministry said rains in the area could have accelerated the decline, washing away radioactive materials.
The samples were collected in June, but the findings were not published earlier. The ministry said it will continue monitoring of the radiation levels.
Three of six nuclear reactors at Fukushima underwent meltdown due to power outage caused by the earthquake and tsunami in March 2011. The incident was the worst nuclear disaster since Chernobyl, though it has resulted in no immediate fatalities. About 140,000 people were evacuated from the contaminated area, and the cleanup of the disaster is estimated to be completed in 2051.