After the Setagaya-ku, Tokyo's radiation scare turned out to be radium, what could this be this time in Kashiwa City, Chiba Prefecture, where the radiation level remains elevated?
From Nikkei Shinbun (11:24PM JST 10/21/2011):
Kashiwa City in Chiba Prefecture announced on October 21 that the very high radiation of 57.5 microsieverts/hour was detected on the land owned by the city in Nedo District. The cause of the high radiation is unknown. Since the measured number is extremely high, "It is hard to believe this is from the Fukushima I Nuclear Plant accident", says the city's general affairs department.
It is a vacant lot, and 57.5 microsieverts/hour radiation was detected 30 centimeter below the surface of the ground. The radiation dropped to 0.3 microsievert/hour at 10 meters from the spot. The city has designated the 3-meter radius from the spot as off-limit, and is planning to remove the soil sometime after October 24.
The city had received information from a citizen on October 18 that there was a high radiation spot, and the city tested on its own.
The city's announcement is here (in Japanese). According to the announcement,
The city received a telephone call on October 18 from the neighborhood association that there was a high radiation spot;
On October 19, the city measured the radiation at the location which is owned by the city. Radiation exceeding 10 microsieverts/hour was measured at a particular spot;
On October 20, with the officials of the neighborhood association present, the city measured the radiation again. The radiation survey meter of the city couldn't not measure over 10 microsieverts/hour;
On October 21, the city asked the Chiba Prefectural Environment Foundation to measure the radiation. After digging the soil at the location, maximum 57.5 microsieverts/hour at 30 centimeters below the surface was confirmed.
The yellow marker is where the spot is (from a tweet by a resident):
It's a thin strip of land in the middle of residential/commercial mixed neighborhood.