In this Democracy Now interview, Paul Gunter claims that the fuel for reactors #4, #5, and #6 were taken out of the reactors and stored in the spent fuel pools. If true, that compounds the problems because #4's pool is supposedly emptied of water. Here is what he said:
PAUL GUNTER: Well, obviously, right now, there is a lot of contradictory information. I think that what’s most important to understand is that among these six units at Fukushima Daiichi, Units 4, 5 and 6, the fuel in the reactor core was taken out of the reactor vessel, taken out of containment, and placed in these rooftop spent fuel pools. So all of the radioactive inventory was moved. We’re very concerned about this very large volume of radioactive material that is now in a conflict of information in its state of, you know, no water or water. But clearly, right now, there is a serious danger of a full core meltdown outside of containment at Unit 4. This could occur at Unit 5 and 6, and we still have the crippled reactors at 1, 2 and 3.
It is worth reading the entire transcript or listening to the interview.
Also of note is the lengthy and well documented essay, "Nuclear Apocalypse in Japan
Lifting the Veil of Nuclear Catastrophe and cover-up" by Keith Harmon Snow