RCMP are once again warning of the potentially fatal effects of counterfeit drugs after traces of the toxic W-18 chemical were found in an Oxycodone tablet seized near Kindersley.

Mounties say officers with the Kindersley detachment were notified of the W-18 finding Friday by Health Canada. One of three counterfeit Oxycodone pills seized during an April 2016 traffic stop on Highway 21, south of Kindersley, contained the synthetic research chemical, police said in a media release.

W-18 is sometimes used as a cutting agent for opioids, like fentanyl. It was added to the Controlled Drugs and Substances Act in November.

The chemical can be lethal in small doses, according to RCMP.

“Street drugs are often represented as one thing while being something completely different,” RCMP stated. “Mixing various agents can create a deadly combination.”

Fentanyl, cocaine, ecstasy and heroin were also seized during the traffic stop.

One person has since pleaded guilty to possession for the purpose of trafficking and been sentenced to 16 months in relation to the stop. Another person is set to stand trial in February.

Health care authorities in Kindersley have been notified of the test results, according to RCMP.

CORRECTION: An earlier version of this story stated W-18 had yet to be added to the Controlled Drugs and Substances Ac. We regret the error.