CHIBA — The science ministry said Sunday that the high radiation detected on city-owned land in Kashiwa, Chiba Prefecture, is emanating from cesium that was probably ejected by the crippled Fukushima nuclear plant, contradicting the city’s earlier claims.

When the Kashiwa Municipal Government first got wind of an airborne radiation reading of 57.7 microsieverts per hour at the site, it said the radiation was unlikely to be related to the Fukushima disaster as it was in such a tiny area.

On Sunday, the ministry and city workers found a side ditch near the spot during a joint survey and said it is highly likely that rainwater tainted by fallout from the Fukushima plant flowed into nearby soil.

“The possibility is high that cesium carried in rain water condensed and accumulated in the soil,” said Takao Nakaya, heads of the science and education ministry’s radiation regulation office.

Part of the ditch, which is about 30 cm deep, was broken and the water seems to have leaked from there, ministry officials said.

“We’d like to take (the finding)s back to the office and start decontamination work as soon as possible,” Nakaya said.

Local residents said that they were deeply concerned.

“This was a place where children always played around. I’m worried about whether the radiation had any effects on the children,” said Shigeru Ono, 74.

Earlier surveyors who dug deeper into the hot spot soil recorded stronger radiation, leading some experts to speculate the tainted soil came from elsewhere and was deliberately buried.

But the ministry confirmed the same day that rainwater is leaching from the ditch and into the soil at the hot spot.

Up to 276,000 becquerels of cesium per kilogram of soil was detected 30 cm below the surface there Friday after abnormally high airborne radiation was detected earlier in the week, the city said.

“If fallout from the Fukushima plant naturally falls onto the ground, it’d be unthinkable that the radiation level would be higher deep in the soil than on the surface,” said Masako Sawai, researcher at Citizens’ Nuclear Information Center, a Tokyo-based antinuclear activist group, before the ministry press conference Sunday.

Earlier this month, residents in Setagaya Ward were alarmed after a similarly small hot spot was found at the fence of a house. The source of the radiation, however, turned out to be bottles of radium left under the house decades ago.