An alarming new report is raising more concerns about e-cigarettes, particularly the vaping products that come from unregulated sources.

The details come from an investigation published Friday by NBC News, which commissioned a top cannabis testing facility to test a sample of 18 THC vaping cartridges. The cartridges were obtained from both legal dispensaries and unlicensed dealers.

The three cartridges that were procured from legal dispensaries based in California included “no heavy metals, pesticides or residual solvents like Vitamin E.” The same could not be said, however, for the products bought from the illicit market.

According to NBC, “13 out of the other 15 samples from [illicit market] THC cartridges were found to contain Vitamin E.”

The testing facility commissioned by NBC also tested 10 of the unregulated cartridges for pesticides, with all 10 coming back positive.

“The products all contained myclobutanil, a fungicide that can transform into hydrogen cyanide when burned,” NBC reported.

The Vape Crisis Keeps Getting Worse

The report serves as the latest piece of disquieting news surrounding vaping. At least 12 people are in the United States are believed to have died from lung illnesses stemming from e-cigarette use, with hundreds of other non-fatal vape-related cases currently being investigated.

But those cases are still shrouded in mystery, as officials don’t yet know what product or substance is the exact cause of the illness. The Center for Disease Control and Prevention has emphasized that vaping “exposes users to many different substances for which we have little information about related harms – including flavorings, nicotine, cannabinoids, and solvents.”

The ongoing mystery coupled with the mounting illnesses has prompted government officials to consider bans on certain e-cigarettes, which have grown in popularity in recent years as the products have been billed as a safer alternative to conventional cigarettes. A pair of House of Representatives subcommittees held hearings earlier this week on e-cigarettes, which included testimony from both doctors and the parent of a teen who fell ill from vaping.

Some of the testimony focused on the risks surrounding flavored e-cigarettes, which are seen as inappropriately marketed to teenagers. Those products have drawn particular scrutiny from government officials, including the Trump administration, which said earlier this month that it would seek to ban most flavored e-cigarettes. State governments have similarly followed suit.

Last week, New York Gov. Andrew Cuomo said he wanted the state to ban flavored tobacco vaping products, a move that followed a similar announcement by Michigan Gov. Gretchen Whitmer.

Walmart, the world’s largest retailer, also announced last week that it would stop selling e-cigarettes, citing the “uncertainty” surrounding the products.