Japan Nuclear Crisis: Radiation Detected on Land and at Sea Outside Plant as Officials Fear Partial Meltdown

March 28, 2011— -- Radiation from Japan's crippled nuclear reactors has now contaminated the ground and the sea surrounding the Fukushima Daiichi complex, as officials fear that some of the reactors may already be in partial meltdown.

Power company officials admitted today that plutonium has been found in the soil near the plant, although officials stressed that the amount of radioactive material was small and not a threat to the public, the Associated Press reported. Radiation has also been detected as far as a mile north of the plant.

Inside the plant, video captured smoke billowing from reactors two and three, a visible sign of the struggle there.

All the reactors have so far held the intense pressure, although there are cracks in the concrete and steel components.

Radioactive water has been found in all four of the reactors at the plant, which workers are continuing to pump out. Officials said the contaminated water must be taken out before workers can restart and restore the plant's cooling system. Workers in the plant are sleeping in hallways and meeting rooms, protecting themselves from the radiation with lead sheets.

"Apparently, there is a crack, a crack in the vessel by which radiation is escaping," U.S. physicist Michio Kaku said. "This could mean that if the core begins to melt, we could have a steam explosion, a hydrogen gas explosion like Chernobyl."

The news comes a day after officials apologized for an inaccurate reading of a major increase in radioactivity, causing a panic that led workers to flee the plant. The inaccurate reading was confirmed as a mistake Sunday night by operators at the plant.

"The number is not credible," Tokyo Electric Power Co. spokesman Takashi Kurita said. "We are very sorry."

The mistake prompted harsh criticism from the government.

"Such a mistake is not something that should be forgiven or acceptable," government spokesman Yukio Edano said.

ABC News went to the headquarters of Tokyo Electric Power Co. to ask Kurita about the latest in a number of conflicting reports coming from the Fukushima Daiichi plant.

"We are so sorry to inconvenience everybody," he told ABC News. "We are trying to stabilize the situation. We are trying to give out the most accurate information."

Asked why more help has not been brought in, he said, "I agree with you, actually, but we are doing our best. But at the same time, the government and also many companies and economists and defense force and fire department, all sorts of people have been supporting us to calm down the situation."

Radioactive Water Might Be Leaking Into Ocean

Hidehiko Nishiyama, a spokesman for the Nuclear and Industrial Safety Agency, told reporters that radioactive water may be leaking into the ocean.

New radiation readings indicate that the contamination in the ocean has spread to about a mile north of the plant, the Associated Press reported.

On Sunday evening, Nishiyama acknowledged the challenges that are facing the relief effort but insisted is stabilizing.

"The problem is that right now nobody can reach the turbine houses where key electrical work must be done. There is a possibility that we may have to give up on that plan," he said.

Meanwhile, experts at Japan's Nuclear and Industrial Safety Agency said that the radioactive materials could be leaking directly from the reactor core, which would indicate a breach.

Physicist Kaku said if radiation levels get too high, that's the point of no return.

ABC News' Molly Hunter, David Wright and the Associated Press contributed to this report