Radiation levels spiked at the Fukushima nuclear power plant, and according to some reports, forced workers trying to cool down the reactors to temporarily evacuate the plant. Other reports suggest that workers have either returned to the plant, or that a skeleton crew was able to remain.

If the workers are forced to abandon the plant entirely, it’s likely the cooling efforts, which are not automated, will not be able to continue, increasing chances of a complete meltdown or the exposure of spent fuel rods in storage facilities—both of which would result large and dangerous releases of radiation into the environment. “I’m very concerned that the ongoing activities may become more and more challenging if rad levels continue to increase for workers engaged in manual action at the site,” Edwin Lyman, a nuclear expert at the Union of Concerned Scientists, said yesterday. “I don’t know–if there had to be an evacuation of all workers–if the jerryrigged cooling that they now have could be maintained,” Attempts to cool at least part of the plants using water from helicopters were abandoned due to either risk of hydrogen explosions at the plant, or high exposures to radiation.

There are also reports now that containment vessels in two of the reactors have cracked, releasing radioactive steam. It’s not clear how bad the breaches are, or how much radiation is being released.

Peter Fairley contributed to this post.