A total of four Hawaii residents — one per county — have fallen ill after using electronic smoking devices, the Hawaii Department of Health reported Friday.

Two of the patients are adolescents. All have reportedly recovered after their hospitalizations.

“The public should refrain from using these products, regardless of whether they contain nicotine or THC,” said Hawaii Department of Health Director Bruce Anderson.

The Hawaii announcement follows the latest development in a national investigation into a string of vaping-related illnesses and deaths, which have claimed 42 lives.

As of Nov. 13, there were 2,172 cases of e-cigarette or vaping associated lung injuries across the country.

The national Centers for Disease Control and Prevention marked vitamin E acetate as a common culprit: Fluid samples from the lungs of 29 U.S. patients contained the chemical, which is a synthetic version of vitamin E often used in e-cigarette liquid. Vitamin E is safe to ingest, but its synthetic counterpart appears to be dangerous when inhaled.

Each case revealed vitamin E acetate “at the primary site of injury within the lungs,” according to the CDC.

Both THC and nicotine were found among all cases of injury, with THC identified in 82% of the samples and nicotine identified in 62% of the samples.

“The latest national and state findings suggest products containing THC, particularly from informal sources like friends, or family, or in-person or online dealers, are linked to most of the cases and play a major role in the outbreak,” the CDC stated.

The CDC is continuing its investigation into other substances that could be attributed to the outbreak of illnesses, now dubbed EVALI.

“E-cigarette, or vaping, products should never be used by youths, young adults, or women who are pregnant,” the CDC website says. “Adults who do not currently use tobacco products should not start using e-cigarette, or vaping, products. There is no safe tobacco product. All tobacco products, including e-cigarettes, carry a risk.”

E-cigarette usage rates reported by Hawaii youth are significantly higher than the national average, particularly on neighbor islands.