Hawaiian store owners said people on the Pacific island US state are rushing to get iodide pills to protect against radioactivity from a quake-crippled Japanese nuclear power plant.
While officials on Hawaii -- 4,000 miles (6,500 kilometers) east of Japan -- warned that taking potassium iodide could have unwanted side effects, health food and other stores said they had sold out of stocks over the weekend.
"As soon as people heard about the first explosion (in Japan), people wiped our shelves clean," said Amber Simone of the Honolulu branch of the Down to Earth health food store chain, which has five branches.
"We've been inundated," she added, saying her store had a waiting list of 184 people, and every few minutes another five to 10 people were being added.
The store usually carries bottles of iodine supplements for people with thyroid issues, but it is being seized upon as a possible way to protect against radiation.
Potassium iodide "is a salt of stable (not radioactive) iodine. Stable iodine is an important chemical needed by the body to make thyroid hormones," a US Centers for Disease Control (CDC) fact sheet explained.
Radioactive iodine from a nuclear event can pollute the air and contaminate the food supply. Experts believe many cancer cases after the Chernobyl disaster in Ukraine in 1986 were linked to milk from contaminated cows.
Thyroid glands quickly absorb radioactive iodine, causing damage. But iodide pills can block radioactive iodine from being taken into the thyroid gland, according to the CDC fact sheet.
Meteorologists say it is impossible to predict the strength or path of radioactivity from Japan's quake-hit Fukushima power plant, although some suggest that the jet stream will blow it eastward toward the US West Coast.
Celestial Natural Foods on the main island of Oahu's north shore sold out of its stock of iodine supplements on Tuesday, said store manager Melody Allen.
Customers have been buying supplements with smaller amounts of iodine such as bladderwrack, red clover burdock, kelp, and several types of dried seaweed, she said. People were calling with inquiries every half hour, she said.
The Hawaii Department of Health is warning Hawaii residents not to take potassium iodide pills as a precaution against radiation exposure unless told to do so, because of the side effects.
"If a need should arise for residents to start taking potassium iodide to guard against effects of radiation exposure, the Hawaii State Department of Health ... will inform the public," said interim health director Loretta Fuddy.
"We do not anticipate this need," she added.