Radiation levels shot up in Tokyo and its vicinity Tuesday

Radiation levels shot up in Tokyo and its vicinity Tuesday following the nuclear accident at the Fukushima No. 1 nuclear power plant in northeastern Japan that was triggered by last week's massive earthquake and subsequent tsunami, local governments said.

But those levels did not pose immediate danger to human health, the Ministry of Education, Culture, Sports, Science and Technology said.

In Tokyo, small amounts of radioactive substances, such as iodine and cesium, were detected, the metropolitan government said.

In Ibaraki Prefecture, adjacent to Fukushima Prefecture where the troubled Fukushima No. 1 nuclear power plant is located, the amount of radiation at one stage reached 5 microsievert per hour, 100 times higher than usual, the Ibaraki prefectural government said.

In Kanagawa Prefecture, the radiation level shot up 10 times higher than usual.

In Saitama, capital of Saitama Prefecture, the amount of radiation reached 1,222 nanosievert per hour -- a figure about 40 times higher than usual.

In Ichihara, Chiba Prefecture, the amount of radiation showed a two- to four-fold increase, the Chiba prefectural government said.

The amount of radiation rose to 1.318 micro sievert per hour -- a figure 33 times bigger than usual -- in Tochigi Prefecture's capital of Utsunomiya, the Tochigi prefectural government said.

The science ministry said it had asked prefectural governments to observe radiation levels as frequently as possible.

Meanwhile, Chief Cabinet Secretary Yukio Edano said the radiation level reached 400 millisievert per hour near the No. 3 reactor at the Fukushima No. 1 plant Tuesday morning. The amount is 400 times higher than the allowable limit for citizens in a year.

On Monday, the radiation level near the No. 3 reactor peaked at 3,130 microsievert or about 3 millisievert per hour.

Steam containing radioactive substances was released from the Fukushima No. 1 nuclear power plant as part of efforts to reduce pressures within the reactor container there.

Northerly winds brought radioactive substances from Fukushima Prefecture to Tokyo and its vicinity, nuclear experts said.