Radiation levels rose in Tokyo and some surrounding areas on Tuesday after the nuclear accident at the Fukushima No. 1 nuclear power plant in northeastern Japan, according to local governments. The amount was believed to be about twenty times higher than normal.

Nuclear experts believe winds carried the radioactive substances hundreds of miles.

Tokyo, as well as the Kanagawa and Saitama prefectures (which also reported higher radiation) are about 150 miles away from Sendai, the locale of the damaged nuclear plants.

However, the country’s Ministry of Education, Culture, Sports, Science and Technology assured that the higher levels did not pose an immediate risk to human health.

I received a report this morning that there was an important change of data, Tokyo Governor Shintaro Ishihara said at a news conference. I heard that it will not immediately cause health problems.

Tokyo’s metropolitan government said small amounts of radioactive substances, including iodine and cesium, were detected.

Radiation levels were much higher in regions near the nuclear plants.

For example, in the Ibaraki Prefecture, which is located next to Fukushima Prefecture (the locale of the damaged Fukushima No. 1 nuclear power plant), the amount of radiation at one point reached 5 microsievert per hour, which is 100 times higher than normal, the local prefectural government said.

However, in Kanagawa Prefecture (which is south of Tokyo) the level of radiation rose ten times higher than usual.

In Saitama (just north of Tokyo), the radiation amount reached 1,222 nanosievert per hour – which is about 40 times higher than normal.

Similarly, in Ichihara, Chiba Prefecture (just east of Tokyo), the amount of radiation increased by two to four times the normal level, according to the local prefectural authorities.

In the Tochigi Prefecture (north of Tokyo and closer to Sendai), the radiation figure was 33 times greater than normal.

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 on Tuesday morning -- and amount that is 400 times higher than the permissible limit for citizens in a year.

Edano admitted that the high radiation levels detected after the explosions at the No. 2 and No. 4 reactors ‘‘would certainly have negative effects on the human body.’‘

Prime Minister Naoto Kan beseeched people living between 20 and 30 kilometers from the Fukushima plant to remain indoors. Japanese residents who live within the 20 kilometer radius have already been evacuated.

‘‘The danger of further radiation leaks [from the power plant] is increasing.’’ Kan warned at a press conference, while asking that people ‘‘act calmly.’‘

Tokyo Electric Power Co (TEPCO), which operates the power plants, said the problem could deteriorate into a critical ‘‘meltdown’’ situation after part of the containment vessel at the No. 2 reactor was damaged by what is believed to be a hydrogen explosion.

Kan has also criticized TEPCO for its management of the crisis at Fukushima.

‘‘The TV reported an explosion. But nothing was said to the premier’s office for about an hour,’’ a reporter overheard Kan saying during a meeting with power company executives at its head office. ‘‘What is going on?’‘

Moreover, Kan has ordered the company not to remove its employees from the power plant.

‘‘In the event of withdrawal from there, I’m 100 percent certain that the company will collapse,’’ he said.

‘‘I want you all to be determined.’‘