LAS VEGAS — A popular line of cannabis-derived CBD products was found to be tainted with a dangerous synthetic cannabinoid known to cause anxiety, agitation, and psychosis.

The discovery by researchers at Virginia Commonwealth University prompted them this week to warn e-liquid users of the danger and to call for government oversight of unregulated CBD products.

The manufacturer of the allegedly tainted products, Diamond CBD, markets a line of hemp-based oils and e-liquids, the best known of which is Chong's Choice, endorsed by the 1970s comedian and celebrity stoner Tommy Chong of Cheech and Chong. The company, owned by PotNetwork Holdings, also markets the Liquid Gold brand.

Diamond CBD's chief executive officer said he was surprised to learn about tainted e-liquids. "Our products are all subject to third-party testing," said Kevin Hagen, who was in Las Vegas attending the MJBiz Con, the world's largest marijuana and hemp business conference. "I suppose any type of product could be tampered with or modified by someone with a syringe." He says the company is looking into the case and doing all it can to ensure the best-quality product is on the market.

CBD, or cannabidiol, is one of the more than 100 compounds produced by the cannabis plant that scientists are investigating. The FDA recently approved the compound, which doesn't provide the high of the better-known THC, to treat some rare forms of childhood epilepsy.

It is increasingly being sold as a cure-all to treat a myriad of ailments from anxiety to pain and cancer. Though anecdotal evidence of CBD's therapeutic effects are numerous, there are no clinical studies offering proof that CBD works for anything but epilepsy.

With the exception of the government-approved Epidiolex, all commercial forms of CBD are considered to be illegal by the federal government and are therefore unregulated.

The researchers at Virginia Commonwealth, in Richmond, recently tested a suite of nine Diamond CBD products. In two separately purchased samples, they found the synthetic cannabinoid 5F-ADB in Liquid Gold Strawberry e-liquid. The toxic compound also was discovered in Liquid Gold Jungle Juice e-liquid and Diamond CBD Vape Additive.

In another sample of the vape additive, they found Dextromethorphan (DXM), a chemical normally used as a cough suppressant.

"The finding of both 5F-ADB and DXM were both unexpected," said researcher Justin L. Poklis, who was the primary author of the article published in the journal Forensic Science International.

"There was no indication on the website, box, or labeled e-liquid containers to indicate that these products contained any psychoactive substance other than CBD," Poklis said. "There are things that shouldn't be in these products that are potentially dangerous. Somebody really has to step in and actually look at this stuff."

Poklis, of Virginia Commonwealth's department of pharmacology and toxicology, warned of the potential effects of the chemicals found in the Liquid Gold and the vape additive.

"The addition of 5F-ADB and DXM compounds to the CBD products may lead to unexpected psychoactive effects," Poklis said. "The inclusion of these drugs in e-liquids can lead to dangerous consequences, particularly when the users are unaware, and the products are used for therapeutic reasons."