TOKYO (AFP) - High levels of radioactive contamination have been found in soil in the capital of Japans Fukushima prefecture, a study showed Wednesday, prompting calls to make the area a voluntary evacuation zone. Some 307,000 becquerels of caesium per kilogramme (2.2 pounds) of soil was detected in an independent survey conducted on September 14 by a radiological engineering expert and citizens groups. The Japanese governments legal limit is 10,000 becquerels per kilogramme. The contamination is believed to have been caused by radiation that has leaked from the Fukushima Daiichi nuclear plant.