RICHMOND, Va. » The public will have more time to weigh in on a federal proposal to regulate electronic cigarettes and other tobacco products.

The Food and Drug Administration said Friday that the public comment period slated to end July 9 is being extended an additional 30 days to Aug. 8 after getting lots of input on how to regulate e-cigarettes. Those are battery-powered devices that heat a liquid nicotine solution, creating vapor that users inhale. The FDA also proposed extending its authority to regulate cigars, hookahs, nicotine gels and pipe tobacco.

In April, the FDA proposed banning sales of e-cigarettes to anyone under 18, adding warning labels and requiring agency approval for new products. But the FDA didn’t immediately place any marketing restrictions on e-cigarette makers or ban fruit or candy flavors, which are barred for use in regular cigarettes. The agency has left the door open to further regulations, but says it wants more evidence before it rushes into more restrictions.

In addition to mandating warning labels that say nicotine is an addictive chemical, the rules would require e-cigarette makers to disclose their products’ ingredients. They would not be allowed to claim their products are safer than other tobacco products. In addition, they couldn’t give out free samples or sell e-cigarettes in vending machines unless they are in a place open only to adults, such as a bar.

The agency has received more than 33,700 comments on the proposal. By comparison, it received around 176,000 comments on potential menthol cigarette regulations during a 120-day comment period.

There is no timetable for when the FDA will issue its final rules, which could be shaped by the public input the agency receives. Many believe the final regulations will wind up in court.

The market for e-cigarettes has grown from thousands of users in 2006 to several million worldwide and reached nearly $2 billion in sales last year. Tobacco companies have noticed that e-smokes are eating into cigarette sales, and they have jumped into the business, too.

Smokers like e-cigarettes because the nicotine-infused vapor looks like smoke but doesn’t contain the thousands of chemicals, tar or odor of regular cigarettes. Some smokers use e-cigarettes as a way to quit smoking tobacco, or to cut down. Scientists haven’t finished much research on e-cigarettes, and the studies that have been done have been inconclusive.

Still, some wonder whether e-cigarettes keep smokers addicted or hook new users and encourage them to move on to tobacco. And others warn that the FDA regulations could have unintended consequences.