New smokeless, electronic cigarettes have become increasingly popular in the U.S., with smokers buying the devices online even as the U.S. Food and Drug Administration (FDA) has intercepted some shipments of the products, saying that they are unapproved drug-delivery devices.

The New York Times reported June 2 that the battery-powered devices, which deliver a dose of nicotine and flavorings without burning tobacco, have become popular with smokers looking for an alternative to breathing in hot smoke or avoiding bans on indoor smoking. Most are purchased online, but also are for sale in mall kiosks and other retail outlets for about $100-$150.

However, the e-cigarettes have neither been evaluated or approved by U.S. regulators, and the FDA has blocked several shipments from China. "These appear to be unapproved drug-device products, and as unapproved products they can't enter the United States," an FDA spokesperson said.

"We basically don't know anything about e-cigarettes," said Richard D. Hurt, director of the Nicotine Dependence Center at the Mayo Clinic. "They've never been tested for safety or efficacy to help people stop smoking."

"It looks like a cigarette and is marketed as a cigarette," added Jonathan P. Winickoff, of Massachusetts General Hospital for Children and chair of the American Academy of Pediatrics Tobacco Consortium. "There's nothing that prevents youth from getting addicted to nicotine."

The e-cigarettes contain propylene glycol, which is an ingredient of antifreeze and is generally seen as safe in food, although experts don't know if inhaling the chemical is safe.

Australia and Hong Kong have banned e-cigarettes, while other countries regulate them as medical devices. The current FDA tobacco-regulation bill in Congress could give the agency broader power to regulate the devices.

"The FDA has the power to regulate Nicorette gum and the like because it is marketed as a smoking-cessation product," said Kip Schwartz, a lawyer for manufacturer Smoking Everywhere, who asserts that the agency has no such power over e-cigarettes because manufacturers make no such claims.