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When U.S. officials found vials of white powder aboard a Japanese freighter bound for the U.S. a year or two ago, they assumed it was heroin. But the substance turned out to be far more dangerous than any narcotic. Laboratory tests revealed the powder to be tetrodotoxin, one of the world's deadliest poisons. Tetrodotoxin is familiar to some Hawaii residents because it's the poison carried by pufferfish, porcupine fish and boxfish, all common in Hawaiian waters.

Most of us who live here know not to eat these fish, but a few individuals are either unaware of the danger or think they can beat the odds.

Some have suffered the consequences. In Hawaii, seven deaths have occurred from pufferfish poisoning. In Japan, many have died from pufferfish poisoning because of a popular dish called fugu. Fugu is not a Japanese name, but the genus (the first of an organism's two scientific names) of the type of pufferfish Japanese prefer eating. Fugu pufferfish are not found in Hawaii.

Even though there's a risk of being poisoned or killed by fugu, some people consider it a delicacy and pay high prices to get it. Certain methods of fish preparation take out most of the poison. Japanese chefs who prepare fugu must undergo training in special techniques and then pass rigorous tests to be licensed.

Still, fugu chefs don't remove all of the toxin because part of the fun of eating fugu is the induced sense of euphoria. Some also claim it is an aphrodisiac.

Whatever its effects, eating anything that might contain any amount of tetrodotoxin is not worth the risk. This poison is about 10,000 times more potent than cyanide.

Once in the body, tetrodotoxin temporarily blocks nerve conduction. This means a victim's brain continues sending messages to the body (talk, walk, breathe), but the body can't respond. Depending upon the amount eaten, poisoning symptoms range from mild numbness around the mouth to total paralysis.

No medicine can reverse the toxin's nerve blockage, but with breathing assistance, a paralyzed person can survive. The toxin begins to wear off in about 24 hours.

Pufferfish aren't the only animals known to bear tetrodotoxin. Australia's blue-ringed octopus carries it, as do some species of flatworms, parrotfish, starfish, arrow worms, sea squirts, horseshoe crabs, ribbon worms living in oysters and trumpet snails.

And the list continues to grow. California newts, Central American toads and some poison arrow frogs carry this poison. Recently, researchers discovered tetrodotoxin in three species of Taiwan gobies.

How did such a diversity of animals evolve the same poison? They didn't. A specific bacterium on or in the animals manufactures the toxin.

Tetrodotoxin isn't all bad. Medical researchers are optimistic that trace amounts may help control certain types of epilepsy, migraine headache pain and other debilitating illnesses.

But no one believes those vials of tetrodotoxin on the freighter were intended for medical research. Officials fear that bioterrorists were planning to use the poison as a horrific weapon.

This notion seemed far-fetched to me when a reader brought this story to my attention a few months ago. Now it's all too real.