VIENNA - The UN atomic agency said on Tuesday it was concerned that it had not received some information from Japan about its stricken nuclear plant, saying the overall situation remained "very serious."

"We have not received validated information for some time related to the containment integrity of unit 1. So we are concerned that we do not know its exact status," Graham Andrew, a senior official of the International Atomic Energy Agency (IAEA), told a news conference.

The IAEA also lacks data on the temperatures of the spent fuel pools of reactors 1, 3 and 4, he said, though Japan was supplying other updates.

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