Updated

Anyone under 18 years old will be barred from buying electronic cigarettes in Massachusetts and the liquid and gels used in the devices will have to be sold in child-resistant packaging under new regulations approved by the attorney general's office.

The regulations also ban the promotional giveaway or free distribution of e-cigarettes and require that they be kept out of the reach of customers.

Attorney General Maura Healey said the regulations also ban most sales of e-cigarettes except through face-to-face purchases and not through vending machines except in adults-only establishments.

"The growth of the e-cigarette market has posed a serious public health risk to Massachusetts residents and calls for strict oversight to protect our young people," Healey said.

The regulations were filed Friday and most take effect Sept. 25. The packaging requirement is effective March 15, 2016.

E-cigarettes are battery-powered devices that turn nicotine-containing liquid into vapor that is inhaled. Though nicotine can be addictive, e-cigarettes lack the chemicals and tars of burning tobacco.

The tougher packaging requirements are intended to prevent the accidental ingestion of the liquids or gels by children.

Jon Hurst, President of the Retailers Association of Massachusetts said shop owners prefer a single set of statewide regulations rather than a patchwork of regulations that vary by city and town.

Healey said while the statewide regulations set an age limit of 18 for purchasing e-cigarettes, the minimum sales age may be higher in cities or towns that have passed their own restrictions.

E-cigarettes haven't been extensively studied and there's no scientific consensus on any potential benefits or harms from "vaping," including whether it leads kids to become regular smokers.

National data show e-cigarettes have become more popular among teens than regular cigarettes.

A recent government-funded study conducted at 10 Los Angeles high schools suggests that teens who use e-cigarettes are more likely than others to later smoke conventional cigarettes. Whether teens had tried just one e-cigarette or were habitual users isn't known, nor is whether they became heavy smokers or just had a few puffs.

The study doesn't prove that electronic cigarettes are a "gateway drug" but some doctors say it bolsters arguments that the devices should be strictly regulated as proposed by the Food and Drug Administration.

Despite its limitations, the study "is the strongest evidence to date that e-cigarettes might pose a health hazard by encouraging adolescents to start smoking conventional tobacco products," according to Dr. Nancy Rigotti, director of a tobacco research and treatment center at Massachusetts General Hospital.

Rigotti's comments and the study were published last month in the Journal of the American Medical Association.

The FDA in 2014 proposed rules that would ban the sale of electronic cigarettes to minors and would add the devices to the list of tobacco products it regulates.