TOKYO -- Japan's prime minister says the country is handling its nuclear crisis "in a state of maximum alert."

Prime Minister put Naoto Kan told parliament the situation remains unpredictable. The spread of radiation is raising concerns about the ability of experts to stabilize the crippled reactor complex.

With the triple punch of an earthquake, tsunami and damaged nuclear plant, Kan says Japan is grappling with its worst problems since World War II.

One official says the Japanese safety standards were insufficient to protect the plant against the tsunami's power. An Associated Press investigation found Tokyo Electric Power officials had dismissed scientific evidence and geological history indicating the likeliness of a massive earthquake and subsequent tsunami was higher than they believed.

Highly toxic plutonium also has been found in soil outside the plant.

More than 11,000 bodies have been recovered, but the final death toll is expected to exceed 18,000.