PHILADELPHIA (CBS) — Researchers say some teens who use e-cigarettes are trying to intensify the buzz.

Doctors at Yale say a quarter of teens who smoke e-cigarettes use a technique called “dripping.”

The process releases liquids in the device directly onto heating oils.

Health officials say doing this could increase the levels of toxins and carcinogens created when the liquid in e-cigarettes is vaporized at high temperatures.

The U.S. Food and Drug Administration announced its intention to regulate e-cigarettes as tobacco products, but hasn’t yet rolled out its new rules.