It's something experts had been saying for month but authorities had yet admit: All of Fukushima's working reactors saw drops in their water levels sufficient to melt their radioactive cores. This means each reactor has a pool of highly radioactive water in its base, possibly a cracked reactor casing, and worse.

TEPCO official Junichi Matsumoto said at a news conference on May 24, "We can't say for certain, but based on the situation in the No. 1 reactor, it is likely that the water level in these reactors fell below the measured level, according to the Mainichi Daily News.