Tokyo (CNN) -- Radiation levels in a Japanese town outside a government-ordered evacuation zone have exceeded one of the criteria for evacuation, the International Atomic Energy Agency said Wednesday.

The agency said it advised Japan "to carefully assess the situation."

The elevated levels were found in Iitate, a town of 7,000 residents about 40 kilometers (25 miles) northwest of the earthquake- and tsunami-damaged Fukushima Daiichi nuclear power plant, the agency said. The evacuation zone covers a 20-kilometer (13-mile) radius around the plant.

The agency did not say what levels it found in Iitate, but the environmental group Greenpeace said Sunday it had found radiation levels in the town that were more than 50 times above normal.

Though that is far below the level that would cause radiation sickness, it does pose a risk of cancer to residents in the long term, Greenpeace said.