Supplies of potassium iodide, a preventive against radiation poisoning of the thyroid gland, were running low Monday at some manufacturers, as Americans sought protection amid fears that radiation from Japan could head to the U.S.

One leading supplier, Anbex Inc., quickly sold out of its supply of more than 10,000 14-tablet packages on Saturday, said Alan Morris, president of the Williamsburg, Va., company.

He said the closely held firm was getting about three orders a minute for $10 packages of its Iosat pills, up from as few as three a week normally.

"Those who don't get it are crying. They're terrified," Morris said. 

Click here to read more about the increase in sales of iodide pills. 

More On This...

The company tells callers that the likelihood of dangerous levels of radiation reaching the U.S. is low, but some callers, particularly on the West Coast, remain afraid, Morris said.

Interest is also high at Fleming Pharmaceuticals, a St. Louis County company that makes potassium iodide in liquid form. "It actually has been insanity here," said Deborah Fleming Wurdack, a co-owner.

Fleming Pharmaceuticals still has supply, but it expects to run out this week, Wurdack said.

Radioactive iodine can be accidentally released from a nuclear reactor. Infants are especially at risk of injury, as are young children and people with small amounts of iodine in their thyroid.

Yet the risk is thought to be low that radiation released in Japan will reach the US West Coast at dangerous levels.

"Japan has an evacuation area of about 12 miles [19km] from the nuclear plants. Washington state is 5,000 to 6,000 miles away from Japan," said Tim Church, a spokesman for the Washington State Department of Health.

Potassium iodide is a salt that stops the body from taking in radioactive iodine that can be emitted during a nuclear emergency. It fills up the thyroid gland, preventing it from collecting the radioactive material and reducing the risk of cancer, among other things.

Click here to read more on this story from The Wall Street Journal.