What a surprise. Now that PM Kan is out, the government dribbles out the information that it withheld as it de-emphasized and even attacked the reports of high soil contamination as measured by private entities including citizens' groups.
The most contaminated location found so far is Okuma-machi, where Fukushima I Nuke Plant is located: 29,460,000 becquerels per square meter with cesium-134 and cesium-137 combined, 15,450,000 becquerels per square meter if only cesium-137 is counted.
The confiscated/closed zone after the Chernobyl accident is set in locations whose cesium-137 level in soil exceeds 1,480,000 becquerels per square meter. The level of cesium-137 in the location in Okuma-machi is 10 times that of the Chernobyl confiscated/closed zone.
From Yomiuri Shinbun (3:05AM JST 8/30/2011):
東京電力福島第一原子力発電所事故で拡散した放射性物質による土壌汚染の状態を調べた地図がまとまり、２９日に開かれた文部科学省の検討会で報告された。
The soil contamination as the result of the Fukushima I Nuclear Power Plant accident was reported on the August 29 meeting at the Ministry of Education and Science.
立ち入りが制限されている警戒区域や計画的避難区域で、チェルノブイリ原発事故での強制移住基準（１平方メートル当たりの放射性セシウム１３７が１４８万ベクレル）を超える汚染濃度が測定されたのは、６市町村３４地点に上った。住民の被曝(ひばく)線量などを把握するのが狙い。菅首相が２７日、「長期間にわたり住民の居住が困難になる地域が生じる」との見通しを示したが、それを裏付けた。
The survey found 34 locations in 6 municipalities exceeding the level of the confiscation/closed zone of the Chernobyl accident (1,480,000 becquerels/square meter of cesium-137 in soil). The purpose of the survey was to understand the radiation exposure of the residents. Prime Minister Kan said on August 27 that there might be locations where the residents wouldn't be able to return for a long time. The survey data validates the prime minister's comment.
測定結果によると、６月１４日時点で、セシウム１３７の濃度が最も高かったのは、警戒区域内にある福島県大熊町の１平方メートル当たり約１５４５万ベクレル。セシウム１３４と合わせると、同約２９４６万ベクレルとなった。
According to the survey, the highest cesium-137 concentration in soil as of June 14 was in Okuma-machi in Fukushima Prefecture, within the no-entry evacuation zone, at 15,450,000 becquerels/square meter. If combined with cesium-134, the radioactive cesium concentration was 29,460,000 becquerels/square meter.
同３００万ベクレル超となったのは、セシウム１３７で同町、双葉町、浪江町、富岡町の計１６地点に上った。高い濃度の地点は、原発から北西方向に延びており、チェルノブイリ事故の強制移住基準を超える地点があった自治体は、飯舘村、南相馬市を加えた計６市町村だった。同省は約２２００地点の土壌を測定した。
Total 16 location in 4 municipalities (Okuma-machi, Futaba-machi, Namie-machi, Tomioka-machi) exceeded 3,000,000 becquerels/square meter in cesium-137 concentration. The area with the high cesium-137 concentration extends northwest from the nuclear power plant. In total, 6 municipalities including Iitate-mura and Minami Soma City had the locations that exceeded the Chernobyl confiscation/closed zone level of cesium-137. The Ministry measured the soil samples from about 2,200 locations.
Here's the map by Asahi Shinbun, including the locations with cesium-137 concentration of less than 1 million becquerels/square meter.