Currently, the F.D.A.’s tobacco regulations apply to cigarettes, tobacco and smokeless tobacco.

“Further research is needed to assess the potential public health benefits and risks of electronic cigarettes and other novel tobacco products,” Ms. Yao said in a statement.

Health officials say their safety has not been medically proved and the devices could encourage children to take up smoking. Some antismoking advocates, who are simply annoyed to see the gadgets glowing in restaurants and bars, call for a ban on their use in public places, the same ban in force for tobacco products.

The allure is unmistakable. The actor Leonardo DiCaprio was spotted puffing on an e-cig at Chateau Marmont in West Hollywood earlier this year, while the French actress Catherine Deneuve, a longtime heavy smoker, now puffs the electronic version in Parisian restaurants and even during news conferences.

Global sales jumped 30 percent in each of the previous three years to around $2 billion in 2011, with the European market around $650 million, according to a recent analysis by Euromonitor International. Retail sales of e-cigs in the United States reached $500 million last year. Although that is only about 0.5 percent of the overall tobacco market, analysts expect those figures to double this year and continue climbing.

“E-cigarette consumption could surpass traditional cigarettes in the next decade,” said Katherine Devlin, president of the London-based Electronic Cigarette Industry Trade Association. “Growth is exponential and there are no signs it’s slowing down. So there is a huge amount at stake.”

Currently, e-cigs are distributed by more than 100 small and medium-size firms like NJOY and White Cloud. Most are manufactured by a Chinese company, Ruyan, which invented the gadget that heats the nicotine solution into a smokelike vapor. The device, which also can have an LED light to mimic the glow of a burning ash, has been registered for patents in more than 50 countries.