Australians dabbling with so-called “legal highs” are playing a potentially deadly game of Russian Roulette experts warn, following the death of a 17-year-old NSW boy who smoked a synthetic cannabis substance.

Dean Shield, from the NSW Hunter town of Rutherford, was found dead by a drain on Saturday night.

While a post mortem is still pending and his cause of death is yet to be determined, detectives believe he took a substance called “Kronic” in the hours before his body was found.

Two other men, both aged 22, were treated for non-life threating symptoms after consuming the same substance at nearby Telarah.

The incident has prompted authorities to warn of the potential dangers of so-called herbal highs.

In 2013, NSW police cracked down on synthetic cannabis, following a string of deaths.

The body of Dean Shield was found on Saturday evening. (Supplied)

But there are concerns that manufacturers have been avoiding the ban by making subtle changes to the drug’s chemical compounds so they don’t fall into the banned list of ingredients.

The SafeWork Laboratories described the process as akin to playing “Russian Roulette” because users don’t know what chemicals they’re actually smoking.

“There’s no Quality Assurance officer supervising the process – just a criminal only concerned about how much money they can make,” national marketing director for the SafeWork Laboratories Andrew Leibie said.

There are a variety of so-called "legal highs" on the market.

“One batch of drugs may be particularly pure in nature, while another may be contaminated with something else that makes it lethal.

“Despite frequently being labelled as “herbal” or “legal highs”, the reality is that these compounds are entirely synthetic and illegal in all states in Australia.”

Police have urged users to re-think using the so-called legal highs.

“Anyone using any form of drugs is putting themselves at extreme peril,’’ Central Hunter crime manager Detective Inspector Mitch Dubojski said.

Following the death, police raided a Rutherford home and business and allegedly found several bags of Kronic and other synthetic drugs, including “Bankok Betty” and “Red X”.

Dean's family is said to be distraught over his death, with sister Karla telling NBN News he had a "heart of gold".

"He was a good kid with a heart of gold and a contagious laugh," she said.