High levels of radiation leaked from a crippled nuclear plant in tsunami-ravaged northeastern Japan after a third reactor was rocked by an explosion Tuesday, March 15, and a fourth caught fire in a dramatic escalation of the 4-day-old catastrophe. The government warned 140,000 people nearby to stay indoors to avoid exposure.

Tokyo also reported slightly elevated radiation levels, but officials said the increase was too small to threaten the 39 million people in and around the capital, about 170 miles (270 kilometers) away.

In a nationally televised statement, Prime Minister Naoto Kan said radiation has spread from four reactors of the Fukushima Dai-ichi nuclear plant in Fukushima state, one of the hardest-hit in Friday's 9.0-magnitude earthquake and the ensuing tsunami that has killed more than 10,000 people, plunged millions into misery and pummeled the world's third-largest economy.

Officials just south of Fukushima reported up to 100 times the normal levels of radiation Tuesday morning, Kyodo News agency reported. While those figures are worrying if there is prolonged exposure, they are far from fatal.

Kan and other officials warned there is danger of more leaks and told people living within 19 miles (30 kilometers) of the Fukushima Dai-ichi complex to stay indoors to avoid exposure that could make people sick.

"Please do not go outside. Please stay indoors. Please close windows and make your homes airtight," Chief Cabinet Secretary Yukio Edano told residents in the danger zone. "Don't turn on ventilators. Please hang your laundry indoors."

"These are figures that potentially affect health. There is no mistake about that," he said, The Associated Press reports.