Youth who use e-cigarettes as their first method of smoking could transition to smoking regular cigarettes and other tobacco products, according to a new study published in the Journal of the American Medical Association (JAMA).

Researchers surveyed 2,530 ninth-graders from 10 Los Angeles public schools for the study. None of the students had ever used combustible cigarettes before the survey, but those who had previously used e-cigarettes (222 students) were found to be more likely to smoke combustible tobacco during the subsequent year.

“This study indicates that e-cigarettes are introducing many kids to use of and possible addiction to nicotine,” according to a statement from Matthew L. Myers, president of the Campaign for Tobacco-Free Kids. “It also adds to concerns that e-cigarettes could serve as a gateway to use of other tobacco products, including regular cigarettes.”

The study’s goal was to evaluate whether e-cigarette use is associated with the use of three combustible tobacco products, specifically cigarettes, cigars and hookah.

Myers said the study highlights why more must be done to regulate e-cigarettes.

“We cannot allow the tobacco industry to keep addicting kids and create another epidemic with a new generation of tobacco products,” he said in his statement. “The FDA and the White House must act promptly to end this unregulated experiment that threatens our kids’ health.”

Earlier this year, the Centers for Disease Control and Prevention announced that e-cigarette use among high school students tripled from 2013 to 2014, increasing from 4.5 percent to 13.4 percent.

California legislators are evaluating a bill strongly supported by the California Medical Association that would regulate e-cigarettes similar to combustible cigarettes. Policymakers are expected to consider the bill during the ongoing special session on public health ordered by Gov. Jerry Brown.