shelter in place. the t.p.c. group produced chemicals like butadiene, which could damage nervous systems. the e.p.a. is monitoring air quality. we have taken at the moment, as best a defensive position as we possibly can in order to try to get everything initiated as cooling, isolate as much as we possibly can, so that we re not continuing to feed the source of the fire. reporter: we were right outside the burning chemical plant when that second explosion occurred. we saw it. we felt it. it was jarring. officials now say that the mandatory evacuation circle now covers a four-mile radius around the plant. firefighters are now working to put out the fire, so they can figure out what caused it. david. begnaud: courtney zubowski near the scene in southeast texas tonight. thank you, courtney. it is one of the busiest nights ever for travel in the u.s. and for tens of millions of people, the timing could not be worse. two major storms are whipping up
meantime this is fox news alert keeping a sharp eye open for signs of radioactive fallout on american soil. reports say the leading edge of what is believed to be a nuclear cloud has reached the west coast of the united states. some radiation has been detected in southern california leading atomic experts say the first readings are about a billion times lower than levels that would have any impact on public health. trace gallagher is live in los angeles, and trace is that calming some of the fear that is out there. reporter: a little bit megyn. it s harmless now, now we know as we watch fukushima if it totally melts down and spews a radiation cloud into the air we know we are in the path. we are learning the 12-mile evacuation circle around fukushima, it could be permanent and they could expand it. the prime minister in japan saying to those people they should look to relocate. the fire trucks are now back on scene at fukushima trying to cool down the reactors, trying