Teens are easily able to purchase e-cigarettes online because websites that sell the devices do not verify the age of purchasers, a new study concludes.

The University of North Carolina researchers say federal law should require and enforce rigorous age verification for all e-cigarette vendors, as it does for online sales of regular cigarettes.

The researchers asked 11 teens, ages 14 to 17, to buy e-cigarettes from 98 online vendors. The teens were successful 75 times. Of the 23 times sales were rejected, only five were related to age verification. That means almost 94 percent of e-cigarette sellers did not verify their customers’ ages.

“In the absence of federal regulation, youth e-cigarette use has increased and e-cigarette sellers online operate in a regulatory vacuum, using few, if any, efforts to prevent sales to minors,” the researchers wrote in JAMA Pediatrics. “Even in the face of state laws like North Carolina’s requiring age verification, most vendors continue to fail to even attempt to verify age in accordance with the law, underscoring the need for careful enforcement.”

Forty-one states have banned e-cigarette sales to minors, HealthDay reports.

The most current Monitoring The Future survey, an annual survey tracking teen drug abuse among 8th-, 10th,- and 12th- graders, found more teens now use e-cigarettes than traditional tobacco cigarettes, or any other tobacco product. The survey found among 10th graders, 16 percent reported using an e-cigarette and 7 percent reported using a tobacco cigarette. Among 12th graders, 17 percent reported e-cigarette use, and 14 percent reported use of a tobacco cigarette.