TOKYO -- Radioactive soil in areas near Japan's crippled nuclear plant have reached the same level as Chernobyl, where a "dead zone" remains 25 years after the reactor in the former Soviet Union exploded.

Soil samples in areas outside the 12 miles exclusion zone around the Fukushima plant measured more than 1.48 million becquerels a square meter, the standard used for evacuating residents after the Chernobyl accident, Tomio Kawata, a fellow at the Nuclear Waste Management Organization of Japan, said in a research report published May 24 and given to the government.

Radiation from the plant has spread over 230 square miles, according to the report. The extent of contamination shows the government must move fast to avoid the same future for the area around Tokyo Electric Power Co.'s Dai-Ichi plant as Chernobyl, scientists said.

"We need to finish this treatment as quickly as possible, within three years at most," Tetsuo Iguchi, a specialist in isotope analysis and radiation detection at Nagoya University in central Japan, said in a phone interview. "If we take longer, people will give up on returning to their homes."

When asked to comment on the report Monday, Tokyo Electric spokesman Tetsuya Terasawa said the radiation levels are in line with those found after a nuclear bomb test. He declined to comment further.

Kawata's study didn't include samples from inside the exclusion zone, where only government and Tokyo Electric staff may enter.