There were other ingredients in the samples, although they didn't appear as consistently. THC surfaced in 23 out of the samples, while nicotine appeared in 16.

The CDC was quick to warn that vitamin E acetate wasn't confirmed as the cause, and that there may be multiple factors involved in the occasionally deadly illnesses. It nonetheless repeated a recommendation to avoid using e-cigs and vapes that included THC, especially from "informal sources" like friends or street dealers. The CDC also stressed that companies shouldn't add the compound to their products until and unless there's a clearer understanding of its effect on lungs. Answers may well be coming -- it's just that officials don't want to take any chances.