Plutonium was found at different locations near the Fukushima Dai-ichi power plant, which authorities have been trying to bring under control since an earthquake and tsunami hit Japan on March 11 and knocked out the plant's cooling system.
"The situation is very grave," Chief Cabinet Secretary Yukio Edano said Tuesday, as reported by AP. "We are doing our utmost efforts to contain the damage."
The traces of the highly toxic substance do not pose an immediate threat to public health, officials said. However, the situation must be watched closely.
The operator of the plant, Tokyo Electric Power Co., said plutonium had been found at low-risk levels in five places around the plant, Reuters reports.
It remains unclear where the higher levels of plutonium had come from, and experts believe at least some may have come from spent fuel rods at the plant or damage to one of the reactors, it states.
About 400 engineers have been working at the plant for weeks to restore its cooling system and prevent a nuclear meltdown. A Japanese nuclear regulatory official recently spent five days at the plant and returned to Tokyo saying the living conditions for the workers are grueling, reports the Los Angeles Times.
"They sleep with just one blanket apiece anywhere there's space — in a conference room, in the hallway, near the bathroom," it states. "Because deliveries of supplies are limited, they get by on very little food: Breakfast is packages of high-calorie emergency crackers and a small carton of vegetable juice; dinner consists of a small bag of "magic rice" (just add bottled water) and a can of chicken, mackerel or curry. There is no lunch — handing out a noontime meal would be too complicated in the crowded two-story building."
The regulatory official questioned if the tough living conditions are interfering with the workers' capabilities and preparedness.
Meanwhile, officials said Monday that radiation readings at one of the plant's nuclear reactors indicate a partial meltdown and possible seawater contamination.
Measurements of water inside the No. 2 reactor suggest a possible fuel rod breach, further complicating efforts to bring the tsunami-hit plant under control, Edano said.
"The radiation seems to have come from fuel rods that temporarily melted down and came in contact with the water used to cool the reactor,” he said, according to the BBC.
"Steam may have condensed... carrying water from within the containment vessel," he said.
Kyodo news said high levels of radiation had also been found in trench of water outside the No. 2 reactor's turbine building, raising concerns that radioactive substances may have seeped into the nearby sea.
Anxiety over contamination levels within Fukushima intensified last week when several workers were hospitalized after coming into contact with dangerous levels of radiation.
Edano criticized plant operator Tepco over safety procedures after the company on Sunday mistakenly reported that radiation readings at the plant were 10 million times higher than normal, instead of 100,000 times.
"Considering the fact that the monitoring of radioactivity is a major condition to ensure safety, this kind of mistake is absolutely unacceptable," Edano said.