BBC News with Gaenor Howells

The United States has expressed

alarm

about the crisis at the Fukushima nuclear complex in Japan, which was severely damaged following the huge earthquake last week. The head of the US Nuclear Regulatory Commission said he thought the cooling pond of the plant's No. 4 reactor was completely dry, leaving its fuel rods exposed. The US energy secretary said the situation appeared to be more serious than the

partial

meltdown at Three Mile Island in Pennsylvania in 1979. Adam Brooks reports from Washington.

The United States military says that none of its personnel in Japan has shown any sign of radiation poisoning, but these were

precautionary

measures. US warships and personnel were being

kept away

from the damaged nuclear power plant, and some air crews were taking potassium iodide, a drug which can help prevent the effects of exposure to harmful radiation.

The Japanese authorities are still struggling to

bring down

temperatures in four reactors at the stricken nuclear plant. Rupert Wingfield-Hayes reports from Tokyo.

The only

certainty

about the situation at the Fukushima nuclear plant is that it's

out of control

. The measures being used by the Tokyo Electric Company and the Japanese government to bring it back under control appear increasingly desperate and

improvise

d. The latest pictures from the site show three of the reactor buildings